Airlines around the world on Monday continued to grapple with contradictory information and ambiguous guidance from the Trump administration and the Department of Homeland Security (DHS) over the executive order that barred citizens of seven majority-Muslim countries from entering the U.S. The travel ban covers Iran, Iraq, Syria, Libya, Somalia, Yemen and Sudan. One ongoing area of confusion centers on whether or not airlines should allow legal permanent residents holding so-called green cards to board flights to the U.S.

In a statement issued January 29, DHS said it was working closely with airline “partners” to prevent travelers targeted by the executive orders from boarding international flights to the U.S. However, it added that it would address green card holders on a “case-by-case” basis, leaving airlines in a position of uncertainty over whether or not to allow those passengers to board a given flight. Lack of clarity over the status of dual-nationality travelers holding citizenship of both the U.S. and one of the seven countries has also led to confusion, leading some airline personnel to turn a blind eye to any non-U.S. passports seen during the check-in process.

“As [DHS] Secretary [John] Kelly previously stated, in applying the provisions of the president’s executive order, the entry of lawful permanent residents is in the national interest,” said the statement. “Accordingly, absent significant derogatory information indicating a serious threat to public safety and welfare, lawful permanent resident status will be a dispositive factor in our case-by-case determinations.”

The guidance comes amid criticism that the White House did nothing to alert the airlines of its plans before announcing the ban at 4:45 pm on Friday. The Trump administration insists that giving any advance notice would have resulted in “a flood” of people attempting to enter the U.S. before the orders took effect.

Asked for comment on the orders’ effect on its operations, American Airlines referred AIN to a travel alert on its web site and DHS for further questions. Neither United nor Delta Air Lines responded for requests for comment. 

While Dubai-based Emirates Airline had to adjust its pilot and flight attendant schedules to ensure none of its employees holding a passport from the seven countries on the list worked any U.S. flights, Abu Dhabi’s Etihad Airways told AIN in a statement that its dispatch department felt no immediate effect. However, it said it has taken steps to ensure “there will be no issues for flights departing over the coming weeks.”

“We are continuing to work closely with the U.S. Customs and Border Protection agency both here in Abu Dhabi and in the U.S.A. on the immigration issues presented over the weekend,” said the Etihad statement. “Our joint interest is on ensuring that compliance and the wellbeing of all passengers is maintained across our global network.

“A number of our passengers have been affected and we are continuing to assist them to identify issues before they fly to the U.S.A. Where permitted, the airline has offered changes or refunds and rebooked passengers, as per our updated policy.”