American Airlines cancelled more than 3,000 flights in the past week as it grounded 300 Boeing passenger jets in order to comply with stepped-up enforcement of safety inspections. The affected airplanes, from Boeing’s MD-80 series, each hold up to 172 passengers and are often described as the “workhorse” of American’s fleet, accounting for nearly half of its planes. So, what was the problem?
Maybe nothing. The current inspections are the result of a rigorous safety review ordered by the Federal Aviation Administration after it discovered that Southwest Airlines had failed to inspect 46 of its Boeing 737s for cracks in the fuselage material. This entailed an audit of airlines’ compliance with government safety guidelines, known as “airworthiness directives.”
The guideline that grounded the fleet of MD-80s at American Airlines relates to a bundle of wires that power a hydraulic pump in the wheel well. Airworthiness Directive 2006-15-15, which went into effect on Sept. 5, 2006, and gave airlines 18 months to comply, requires technicians to better secure the wire bundle to the wall of the well with fasteners at close intervals. (This makes them less likely to catch fire.) Though the MD-80 has been flying since 1980, Boeing regularly issues “alert service bulletins” with recommendations on how to improve safety on its aircraft. The FAA directive was based on a Boeing bulletin from July 2005.
While officials from all agencies have characterized the inspections as abundantly cautious, frayed wires have caused problems before. The extensive investigation into the crash of TWA Flight 800, a Boeing 747, found that an electric fire likely caused an explosion in the fuel tank.
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