At 9:25 a.m. EDT on  Tuesday, Sept. 11, 2001,  the Department of Transportation, via the FAA, ordered the U.S. National Airspace System (NAS) closed to all civil flights at its 460 controlled and 15,000+ non-tower airports. Canada’s Ministry of Transport followed suit within one hour.

Directed from the Air Traffic Control System Command Center (ATCSCC) at Washington Dulles, the FAA’s 17,500 controllers directed the landing of some 4,300 tracked airborne targets and ordered the diversion to Canada of 120 inbound overseas flights, while the remaining inbound airplanes returned to the countries of origin. Nav Canada landed the diverted traffic and its domestic airborne traffic before unplugging its service.

On September 12, crew-only flights began for repositioning and to continue overseas flights diverted to Canada. At 11 a.m. on September 13, DOT Secretary Norman Mineta reopened the NAS to all commercial aviation, with Canada following suit several hours later. Through September 18, in stages that to some appeared arbitrary, most remaining categories of flight were reintroduced.

At press time, the NAS was far from its previous usage or freedom. Typical weekdays see 1.6 million passengers on 40,000 flights, but one week following the terrorist attacks, only 60 percent of commercial flights had returned, and these suffered substantial delays from new attention to security.

No Part 91 VFR flights were allowed, except over Alaska. Chicago Meigs Field and Reagan Washington National Airport were set for indefinite closure. Meanwhile, all airlines announced permanent schedule reductions of at least 20 percent, with additional cuts and possibly even bankruptcies to follow.

As a whole, both the closure and reopening of airspace were executed with extraordinary skill. But logistical demands to the timeline, controversial categories of permitted flight and a vexing lack of information punctuated by outright contradiction caused confusion and anger.

Immediate Global Effect
The grounding order was released to the Air Route Traffic Control Centers at 9:25 a.m. and was promulgated by radio and ACARS. Company networks augmented the grounding order to their own fleets. By 2:07 p.m. the final continental U.S. airliner that was airborne during the grounding order had landed. But as late as 10:45 p.m., Honolulu took 1,500 passengers diverted on flights from Korea, Japan, New Zealand and Australia.

With regional exceptions, commercial carriers continued to the first suitable landing field, which in most cases was their destination, but individual companies were more stringent. Continental ordered 100 diversions. Aircraft gate parking at major airports filled within minutes and additional forced landings stacked on taxiways, choking movement on ramps.

Clifford Mackay, chief executive of the Air Transport Association of Canada, said 70 flights were diverted to the east coast of Canada and 30 to the west, with the remainder to central provinces. Passengers were processed through immigration and customs and their bags searched. Emergency housing was provided for stranded passengers.

Some American Airlines transatlantic flights landed in Gander, Newfoundland, and Halifax, Nova Scotia, while a US Airways flight bound for Seattle from Philadelphia landed at tiny Willard Airport in Illinois. In Whitehorse, the far-north capital of the Yukon, two Korean Air jets landed under escort of Canadian fighters, diverted from Alaska and low on fuel.

Los Angeles International Airport, San Francisco and Boston Logan were evacuated. The Kennedy Space Center in Florida secured its four space shuttles using methods designed to shield them from hurricanes.

Airports and airlines based in Japan, Hong Kong, Singapore, China, Taiwan and South Korea grounded flights, with 170 cancellations at Tokyo Narita alone. British Airways canceled all flights to and from the U.S., while the UK government banned commercial traffic over London, as did Belgian authorities with traffic to overfly Brussels.

At the grounding order, Air France recalled seven oceanic flights and Lufthansa instructed Atlantic flights in transit to return to their origin, while Iberia ordered its four airplanes en route to the U.S. to fly to Canada or return to Spain. Sabena and Finnair recalled three flights, while SAS ordered the crews of four U.S.-bound flights to divert to Iceland.

Poland’s LOT Airlines recalled two airplanes en route. Israel closed airspace to all carriers except flag carrier El Al. British Airways suspended flights to Israel and to Islamabad, Pakistan.

Southwest Airlines began to charter buses, though its point-to-point routing left its passengers and crew relatively unaffected among the majors. South- west had only three aircraft required to land at other than the intended destinations–one at Colorado Springs, Colo.; another at Moline, Ill.; and a third at Grand Rapids, Mich.
The U.S. Postal Service continued delivery but removed guarantees for express mail, while FedEx and UPS aircraft remained grounded. Amtrak canceled all Northeast corridor train service, and Greyhound canceled bus operations at all stations within one mile of federal office buildings. But Amtrak resumed service by 6 p.m. and carried nearly twice the typical load and subsequently added an extra 30-percent capacity the next day. Greyhound, with 2,300 buses each equipped with 52 seats, returned to substantial operation on September 12.

Military Controls Skies
In conjunction with the Depart- ment of Defense (DOD), the North American Aerospace Defense Com- mand (Norad), Transport Canada and the FAA’s ATCSCC, key procedures of a plan called Security Control of Air Traffic and Air Navigation Aids (SCATANA) were launched, without officially invoking that plan by name. The plan was issued in June 1971 to replace the Emergency Security Control of Air Traffic (ESCAT), and the Cold War original, Security Control of Air Traffic during Electromagnetic Radiation (SCATER). These plans are not publicly acknowledged to have been field tested since fall 1962.

Each plan was designed to ground all non-military air traffic to diversionary airports following the confirmation of a defense emergency, and activate an emergency messaging plan via the Federal Communications Commission. A wartime air traffic priority list (WATPL) clears the National Airspace System for the “priority one” President of the U.S., Prime Minister of Canada, their national security staffs, aircraft engaged in continental defense, retaliatory aircraft, refueling tankers and airborne command posts.

U.S. air defense forces have trained to intercept and, potentially, destroy a passenger airliner, but only when flying outside the Air Defense Identification Zone (ADIZ) guarding the coastal U.S. Even then, the shootdown order requires Presidential approval.

At the time of the terrorist attacks, Norad had fighter jets on alert at seven bases around the continental U.S., primed to be airborne within 15 min of the scramble order. At 8:38 a.m. Norad received word that an airliner had been hijacked outside Boston. Six minutes later, two F-15 Eagle fighters from Cape Cod’s Otis Air Force Base were ordered airborne. But at 8:45 a.m. the American 767 crashed into the North Tower of New York’s World Trade Center. The F-15s were airborne at 8:52 a.m. When United Flight 175 hit the South Tower at 9:06 a.m., the F-15s were 70 mi short of Manhattan.

At approximately 9:10 a.m., the DOD learned that another hijacked airplane ( American Airlines Flight 77) might be inbound to Washington. At 9:35 a.m. two F-16 Fighting Falcons took off from Langley Air Force Base, some 150 mi southeast of D.C., but the 757 struck the Pentagon five minutes later.

The F-16s were in position over Washington in time to engage the fourth hijacked airplane, if necessary. That airplane, United Flight 93, also a 757, crashed southeast of Pittsburgh. Four days later, Vice President Cheney acknowledged that the F-16s had been authorized by President Bush to shoot down both 757s if they could not be diverted. Cheney denied any military role in the Pennsylvania crash.

F-15s and F-16s began flying patrol over New York, Washington, Boston, Los Angeles and San Francisco at once, expanding to as many as 20 U.S. cities before the evening of September 12. Patrols prevented civil traffic from occupying the airspace and searched for foreign enemies. AWACS airborne surveillance and tanker aircraft supported the fighter patrols at the coastlines to detect any of the average 7,000 flights that daily approach the ADIZ.

On September 12, a Cessna 185 in violation of the grounding order was escorted to the ground by two F-16s near Martinsburg, W. Va. Unconfirmed reports suggested at least a dozen more general aviation forcedowns. Through 11 a.m. on September 13, the only flights authorized into the airspace were aeromedical, military, firefighting, law-enforcement and hurricane evacuation aircraft operating along certain Gulf coastal states.

In conjunction with the airspace closure, U.S. Coast Guard cutters patrolled ports and closed the waterways within seven nautical miles of Washington National on the Potomac and Anacostia Rivers. Large city water ports were closed to all but essential cargo vessels, which maritime officials boarded and guided. The Coast Guard also surrounded the USS Gates and USS Cole for protection. The two ships are under repair in Pascagoula, Miss.

By midday on Friday, September 14, Norad confirmed at least 100 intercept fighters on “strip alert,” with standby crew for a 15-min launch. Norad and the DOD planned to swell that number quickly, with President Bush receiving congressional approval for the immediate call-up of up to 50,000 reservists, including pilots, controllers and ground crew.

Throughout the grounding, the Global Positioning System signal remained available and at full integrity to all civil users, according to Norad Space Command. The navigational capability can be degraded to civil users in times of defense emergency under a procedure called Selective Availability.

Beginning with the release of limited flights for crew repositioning, some Part 91 operators attempted to circumvent emergency procedures by supplying fake callsigns. The ATCSCC reissued its warning that unauthorized flights would be escorted to the ground and hinted at more grave action. Operators were advised to contact ATC before switching frequencies for any reason and to obtain approval for all course deviations other than emergencies.

U.S. Customs closed indefinitely its General Aviation Telephonic Entry (GATE) program. Flights entering from Canada had to stop for inspection rather than call for
airborne clearance. The Canadian Customs CANPASS program also remained suspended at press time.

On September 14, Part 137 agricultural and crop dusting operations had been allowed to return to the airspace, but two days later these operations were grounded immediately after the FAA revealed credible threats that such aircraft might be used to spread chemical harm. On Tuesday afternoon, September 18, Part 137 ops were reauthorized so long as they stayed clear of Class B airspace
Air Security International now recommends that pilots dress as civilians and the posting of security at corporate aircraft. On Monday, September 17, most FBOs were once again accepting Part 91 IFR flights, but only after requiring crew and passenger screening, usually through the commercial security section of the airport.

Informational Challenge
NBAA president Jack Olcott told AIN within hours of the grounding that NBAA would staff the ATCSCC at Washington Dulles Airport during all open hours, and provide continuous electronic updates.

“Bob Lamond is at the command center, along with our contract
employee Jo Damata, who is with Conwal, under contract with NBAA, to provide this service from the general aviation desk.” After hearing a  radio report of the attacks, Lamond bailed out of his morning commute to NBAA’s downtown Washington offices and entered the Dulles-based ATCSCC minutes later. Federal officials then shut the center to all who followed.

“The airlines were communicating to crews via ACARS, as well as a combination of voice and data,” said Lamond. “Word went out through the en route centers, and from there on it was organized mayhem. Airplanes were directed to the first available airport to land immediately, which may have very well been the airport of destination.” Representatives of the Air Transport Association sat just a few feet away from Lamond.

Early in the afternoon advisories were released to general aviation, but officials acknowledged that preventing VFR takeoffs from uncontrolled airports would be difficult. NBAA patched updates by its online Air Mail to its subscribers. But with surges in Internet traffic, Air Mail distributions were delayed by up to four hours.
By Wednesday night, NBAA supplemented and bypassed Air Mail using direct updates to its Web site (www.nbaa.org). “With the status of the ATC system changing dramatically and hourly, even a two-hour delay can make status information reaching you via Air Mail obsolete,” wrote NBAA’s David Almy.

Almy acknowledged the many plaudits by e-mail and telephone from members for NBAA’s superb and constant update efforts, as well as its help in lifting IFR Part 91 restrictions during a week “we hope never to repeat.” NBAA’s offices opened on Saturday for the first time in a decade.

The FAA was strapped with operational needs and public information sputtered. Its Web site (www.faa.gov), was the referral of choice for a cluster of sites for consumers, pilots and the industry, for both flight and airport status. But the electronic crush left its site inaccessible except for a handful.

When new capacity made it accessible on September 13, the status of the 30 major U.S. airports had never been updated. Each showed a code green, meaning delays of 15 min or less. “Well, that’s accurate,” joked one official, who preferred not to be named. “There’s nothing flying, so there’s not a delay in sight!”

NBAA helped bypass the swamped FAA by processing forms from members willing to offer their  aircraft for emergency airlift. Concurrently, NATA offered the
resources of Part 135 operators to fly the critically injured, as well
as emergency response crews to New York and Washington. DOT Secretary Mineta relayed the offer to the National Security Council.

The FAA published the lists of airports certified to its higher-security review during the phased-in release of aircraft. But it was yet again plagued with electronic jams. The FAA limited access to the operational information system for real-time airport delays; to the e-mail function permitting pilots to make arrival and departure reservations; and to its advisories database.

But the FAA was able to shore up the electronic overload with resources at hand. Within two days of the terrorist attack, a loose system evolved to meet the practical strengths of each organization. Given the media throng approaching the FAA’s senior management, the direct-to-industry reporting continued, but in practice the FAA leveraged the media to reach its users. Media reported live commentary from local airport authorities and became a direct link to pilots and industry. Trade groups repackaged and relayed the information electronically.

Airlines followed suit. United Airlines began releasing airspace status reports by e-mail to its list of Mileage Plus frequent fliers, in
addition to staffing toll-free numbers. Atlantic Coast Airlines, United Express and Delta Connection offered a one-click connection to systemwide status.

NBAA soon followed with a call to membership for a letter and telephone campaign to lobby for full access to the airspace, listing the key contacts in Congress, the DOT, White House, the FAA, the FBI and the CIA. Pete West of NBAA government affairs collected and funneled all responses.

Return and Economic Ripple
The FAA announced plans for the resumption of non-emergency flights, to be phased in in two parts. Parts 121 and 129 (cargo) aircraft diverted to Canadian and U.S. destinations were allowed to return to their original intended destination airport, with their original cargo and passengers, when those airports became available for flight operations. Non-revenue ferry flights could re-position aircraft and flight crews without passengers or cargo. Nav Canada mirrored the plan, with provision for control services.

At 11 a.m. on September 13, commercial carriers were released systemwide subject to the availability of airports that met an 11-point security certification. That morning, the FAA listed fewer than 100. By mid-afternoon the list grew to include at least 200 major airports,  then almost hourly in increasingly large numbers. By 4:30 p.m., 250 commercial airline and cargo flights were aloft over the U.S.

But by early evening Northwest halted operations after security scares. A dozen suspects were taken into custody at JFK and La Guardia by the FBI, which stormed a loaded airliner before it left the gate. Evacuations of airports continued sporadically for the next two days.

With NBAA’s influence and negotiation, Part 91 IFR flights were released into the NAS first for crew only, then with increasing latitude for passenger-carrying flights. All IFR operations were technically allowed by Monday, September 17, but practical limitations on flight-plan clearance and security delays from new passenger and crew checks left airspace usage at levels half the normal measures.

Lingering security delays, and public fear, caused systemwide losses and the cancellation of near-term flights by passengers. The first permanent casualty was Midway Airlines, which had previously filed for bankruptcy protection. Within 12 hr of the terrorist attack it announced its permanent closing and laid off its remaining 1,700 employees.

Two days after the attack, the House of Representatives introduced an emergency $15 billion bailout plan for commercial passenger carriers. A separate bill was introduced to absolve American and United Airlines of any liability stemming from the hijacking and crashes, and to grant all the airlines antitrust immunity to discuss their routes.

By the end of Friday, September 14, 9,822 commercial aircraft and cargo flights had flown, but flights were not expected to return to better than 70 percent of schedules for several weeks. On September 15, Continental Airlines announced a long-term 20-percent reduction in schedule and 12,000 layoffs, with some analysts predicting that it would file for bankruptcy within eight weeks. On September 17, US Airways announced plans to lay off 11,000 employees, 25 percent of its workforce.

UPS and FedEx said 100 percent of flights were operating at all airports, both domestically and internationally, before the weekend, and they expected to clear backlogs by September 17. Crop growers predicted that an indefinite grounding of Part 137 aircraft would lead within weeks to crop diseases and shortages, but ag ops outside Class B airspace were allowed to resume on September 18.

Foreign airlines were reauthorized in stages–beginning, ironically, with those already known to be security risks. It was reasoned they had more advanced passenger screening. Aeroflot resumed its routes from Moscow Sheremetyevo Airport to New York, and Turkish Airlines again began flights from Istanbul Ataturk International to New York.

A week after the attacks, only Reagan Washington National and Chicago Meigs Field remained closed to all traffic, though a host of others were restricted to certain categories of traffic, IFR only or for emergency needs. The Delta Shuttle between Reagan Washington National and La Guardia relocated five daily flights to Dulles by September 16, but as of September 18 its first flight of the day carried only four passengers.

Tropical Storm Gabrielle, with sustained winds of 40 kt, complicated the reopening of airspace, but by September 17 the severe weather system was no longer a threat.
The continued prohibition of VFR flights rocked the airshow industry. As of the first weekend following the attacks, the Reno Air Races had been canceled, costing that city some $40 million in related revenue. Another casualty was the Salinas International Show, along with others affecting one million spectators. Salinas, though, opened its gates to accept donations for victims and the fire and police crews, providing ground entertainment and tours of aircraft that had arrived but were parked idle. In addition to VFR restrictions, the airshow industry stood to lose support from military assets redirected to active deployment.

On the morning of Saturday, September 15, Mary Schiavo, former DOT inspector general, toured the television networks to point out that she had been right all along about the vulnerability of U.S. commercial air travel and airports. Schiavo called for federalization of the security screening process, which is currently delegated to individual airport sponsors. She recommended that air travelers stay away from the system until corrections were made.

Historic Precedent
Though the recent closure of the NAS was by far the largest, the longest in duration, and the most costly in aviation history, the groundings, per se, were not a first. In fact there have been at least three previous publicly known groundings, as well as civil groundings initiated but halted before they took full effect.

During the Cold War, to test continental air defense against manned Soviet bombers, Norad and the Strategic Air Command conducted exercises in each of three consecutive years, requiring civil aircraft groundings ranging from five to 12 hr in all of the U.S., except for Hawaii, and all of Canada.

The first such exercise, Operation Sky Shield, ran from 2 a.m. to 8 a.m. on Sept. 10, 1960. The second and largest, Sky Shield II, was conducted from 1 p.m. on October 14 through 1 a.m. on Oct. 15, 1961. Sky Shield III, held Sept. 2, 1962, was intended to run 5.5 hr beginning at 3 p.m., but an accidental early penetration of the Pacific barrier by a SAC B-52 sent Norad into maximum alert for eight hours.
During Sky Shield II, 2,900 commercial passenger flights were canceled, affecting 125,000 passengers, with much lower but corresponding effects in Canada. At least 559 intercept fighters, including the Voodoo, Delta Dart and Skyray, flew sorties over U.S. cities to engage U.S., Royal Canadian and British Royal Air Force heavy bombers, including the Vulcan, B-47, and B-52, which posed as Soviet forces attacking from over the Arctic.

Missile defenses were activated throughout North America. Aloft, the U.S. Navy provided sea flanks, with radar-equipped WV-2 Super Constellations, nicknamed “Warning Stars.”

The grounding order, which appeared in the Code of Federal Regulations, required all civilian pilots north of the Mexican border, except for Hawaii, to be on the ground or outside the exercise area, “giving consideration to such delay factors as weather and air traffic.” Provision was made for certain operations, “in the interest of health or safety, such as those that may be necessary to prevent, or to provide relief from, fire, flood, or accidents, or for emergency medical treatment or assistance.”

Airports and airlines had been given more than two months’ notice of the Sky Shield II groundings and took advantage to hold public open houses or to perform equipment upgrades. At least 50 U.S. airports displayed 1,800 airliners in static exhibit and conducted walking tours. At New York International (Idlewild, later JFK), 40,000 visitors toured such new airliners as the Astrojet.

At least one publicly known near-grounding was initiated. On Nov. 9, 1979, the SCATANA plan was set into motion after an alert at Norad that was triggered by false reports fed from a computer tape intended for simulations but was mistaken for a genuine attack. The FAA controllers in a limited regional area prepared for immediate grounding of all civil aircraft. Within six minutes, the mistake was discovered and the order rescinded.