Washington ( CNN ) -- The Federal Aviation Administration has proposed a $ 1 million civil penalty against a regional airline for allegedly using improper rivets on cockpit doors , saying the rivets could have damaged wiring and other aircraft components . The agency said Horizon Air operated 22 aircraft for more than three years with the improper rivets , making at least 186,189 flights while the planes were `` unairworthy . '' The FAA discovered the violations last year when Horizon modified a 23rd aircraft with blind rivets , and the plane experienced an incident during a flight because of wire damage , the agency said . Airline takes heat over note on wing . Horizon Air was required to use solid rivets on the doors , but instead used blind rivets , which can be fastened from one side of a panel or structure , `` blind '' to the opposite side . `` We expect airlines to comply with all of our safety regulations and to correct safety defects promptly , '' U.S. Transportation Secretary Ray LaHood said in a statement . Bag delivery fee worth it for some . The FAA said the airline has replaced the blind rivets on its aircraft . Horizon Air , which serves cities in the western U.S. and Canada , has 30 days to respond to the FAA 's proposed penalty . Bobbie Egan , a spokeswoman for Horizon Air , said the airline opted to use an `` alternative and stronger '' rivet , which Horizon believed was acceptable to the FAA . AA chief : Success is only option . `` We believed at the time the alternative rivets were an acceptable substitution . At no time was passenger safety compromised or the integrity of the cockpit door affected , '' she said .
The FAA says Horizon Air operated 186,189 aircraft with improper rivets . The airline made 22 flights while the planes were `` unairworthy , '' the Horizon Air says . The agency is proposing a $ 1 million civil penalty against the regional carrier . FAA says it believed the rivets were OK , `` at no time was passenger safety compromised ''