Officials from the US FAA have proposed the largest fine in the agency's history -- $24.2 million - against American Airlines.

FAA alleges American failed to complete steps outlined in a 2006 airworthiness directive requiring the inspection of wire bundles located in the wheel wells of Boeing MD-80 aircraft.

The AD sought to prevent shorting of wires or arcing in the aircraft's auxiliary hydraulic pump, which could result in the loss of auxiliary hydraulic power or a fire in the wheel well. FAA's directive also aimed to reduce the potential of an ignition source adjacent to the fuel tanks, which when combined with the flammable vapours, could result in a fuel tank explosion.

FAA explains the violations were first detected on 25 Marche 2008, which resulted in additional maintenance work that occurred during the following weeks. After American performed additional maintenance, on 26 March seven of eight aircraft inspected at the carrier's Tulsa maintenance base did not comply with the airworthiness directive.

On 7 April it was determined that eight of nine MD-80s in American's Dallas Fort Worth hub did not comply with the directive.

On 8 April American began grounding the MD-80 fleet to complete inspection and re-work as necessary, which resulted in the cancellation of roughly 3,000 flights.

FAA determined that 286 of American's MD-80s were operated on 14,278 passenger flights while the aircraft were noncompliant. American ultimately completed work required under the 2006 directive.

The MD-80 grounding in 2008 followed the discovery that Southwest Airlines operated 46 of its 737s on 59,791 flights without performing FAA-mandated inspections for fatigue cracks. Southwest ultimately agreed to pay a $7.5 million fine.

Source: Air Transport Intelligence news