The FAA has proposed a $2.425 million civil penalty against Cessna Aircraft following the in-flight separation of portions of skin on the wing of a Corvalis piston single.

The incident occurred last December as an FAA test pilot performed a production audit test flight for the high-performance, all-composite aircraft. Although approximately seven feet of skin on the left wing separated from the forward spar and damaged a fuel tank, the pilot managed an emergency landing at the Cessna facility in Independence, Kan., where the Corvalis is produced.

Investigators said skin separation was the result of “excessive humidity in the factory that prevented the bonded materials from curing properly [and that the aircraft] suffered a significant structural failure in the wing.”

The FAA also issued emergency airworthiness directives grounding 13 specific Corvalises that used wings and parts produced at Cessna’s Chihuahua, Mexico, between Dec. 17, 2009 and Dec. 16, 2010.

The FAA alleges that Cessna failed to follow its FAA-approved quality control system when it manufactured the wings, as well as 82 other parts in the Chihuahua plant.

In response to questions about the incident, Cessna said, “Safety is always Cessna’s top priority [and] we are committed to working closely with the FAA on this matter, which has been isolated to 13 aircraft. We will continue working with the FAA until it is resolved.”

Fifteen U.S. and Canadian aerospace companies have production facilities in nine Mexican cities, in addition to Chihuahua. The shifting of work from U.S. facilities to those abroad, where labor costs are lower, has become an increasingly contentious issue with unions, municipalities and state governments. The number of aerospace jobs in Mexico has increased from 10,000 to 27,000 since 2005 and the value of aerospace exports has jumped in that period from $1.3 billion to $3.1 billion.