AirTran Airways is facing a $250,000 fine from the US FAA for allegedly operating a Boeing 737 on four passenger flights when the aircraft was not in compliance with agency regulations.
The agency states AirTran did not properly repair or test the aircraft's angle-of-attack sensor, which signals a potential loss of lift, after it was struck by lightning on 20 March 2009.
FAA also stated AirTran misused the minimum equipment list (MEL) when it opted to defer the repair and continue to operate the aircraft.
The MEL determines what systems must be in working order to legally fly an aircraft and which items can be deferred temporarily until repairs are made, said FAA.
"Repair or maintenance of a damaged or inoperative angle-of-attack sensor may not be deferred," the agency stressed.
AirTran was acquired by Southwest Airlines earlier this year.