The Federal Aviation Administration (FAA) has approved the Southwest Airlines plan to replace unapproved parts installed on about 50 B-737 airplanes.

The FAA has allowed the airline to continue to operate aircraft with the unapproved part till the replacement, after a technical review determined that the unapproved part wouldn’t affect safe operation of the aircraft.

The aircraft will have to be physically inspected for wear and tear every seven days and the affected parts must all be replaced with an approved part by 24 December 2009.

The carrier will also have to locate and dispose of any other unapproved parts made by the same vendor and report its aircraft inspection results to the FAA on a daily basis.

The unapproved parts are associated with the hinge fittings for the exhaust gate assembly help protect the aircraft flaps from engine heat.

The FAA opened an investigation into the issue after learning on August 21 that the parts had been installed on a number of Southwest Airlines planes.