US operators could face a bill of more than $83 million to comply with a new US Federal Aviation Administration (FAA) airworthiness directive (AD) issued after reports of cracks and skin of Boeing 737 classics.
The FAA estimates the airworthiness directive will impact 629 Boeing 737-200, -200C, -300, -400 and -500 aircraft.
The cracks were reportedly found in the skin and surrounding structure of the aircraft's exterior, under the "number 3" very high frequency (VHF) antenna and aft of the landing gear wheel well. If the cracks are left untreated, the antenna could separate from the aircraft and lead to rapid depressurisation, the FAA says.
To comply with the AD, operators must perform inspections for cracks and corrosion on the aircraft's skin, support, frames, antenna and stringers.
The administration estimates that 387 aircraft more than 20 years old will require their bonded skin panels to be replaced with solid skin panels at a cost of $83 million. Inspections cost up to $695,000 per cycle for the 629 aircraft.
The new AD comes less then two months after the FAA required airlines to perform additional inspections to prevent cracks in other areas of the 737 fuselage.
A lap-joint on a Southwest Airlines 737-300 failed on 1 April, opening a large hole at the fuselage crown during flight and forcing the crew to make an emergency landing in Arizona.