The Federal Aviation Administration (FAA) has approved a plan that would require Southwest Airlines to replace unapproved parts installed on about 50 Boeing 737s and for these aircraft to undergo inspections until fixes are made. The budget airline already has replaced parts on 30 other B-737s. An FAA technical review determined that the unapproved part does not prevent safe operation of the aircraft. Boeing has made a similar determination. “As a result, the FAA has determined that the airline may continue to operate aircraft with the unapproved part until the parts can be replaced, on the condition that each plane must be physically inspected for wear and tear every seven days and the affected parts must all be replaced with an approved part by December 24, 2009,” the FAA said in a statement. The FAA also directed Southwest Airlines to locate and dispose of any other unapproved parts made by the same vendor and to report on the results of its aircraft inspections to the FAA on a daily basis. The unapproved parts are associated with the hinge fittings for the exhaust gate assembly, which help protect the aircraft flaps from engine heat. The FAA determined on August 21 that the parts had been installed on a number of Southwest Airlines planes. The FAA has opened an investigation into this issue.