The Federal Aviation Administration (FAA) has issued an emergency airworthiness directive (AD) concerning approximately 2,000 stored Boeing 737-300-900 series aircraft.

The AD requires inspections of the engine bleed air 5th stage check valve on each engine to identify is there any corrosion. Corrosion of the engine bleed air 5th stage check valve internal parts during airplane storage may cause the valve to stick in the open position.

The AD followed four recent reports of single-engine shutdowns due to engine bleed air 5th stage check valves being stuck open.

“Corrosion of these valves on both engines could result in a dual-engine power loss without the ability to restart. This condition, if not addressed, could result in compressor stalls and dual-engine power loss without the ability to restart, which could result in a forced off-airport landing,” said FAA.