The U.S. Federal Aviation Administration (FAA) Tuesday ordered airlines to inspect their most heavily used older-model Boeing 737 jetliners for fuselage cracks.

Carriers flying the 737-300, 400 and 500 model planes with more than 35,000 flight cycles — or takeoffs and landings — must accomplish the time-consuming electromagnetic checks within five days.

The order stemming from the emergency landing of a Southwest Airlines Co jet last week in Arizona with a hole in its fuselage also requires airlines to go over their older 737s before they hit 30,000 flight cycles.

The most urgent inspections covering about 80 aircraft mostly at Southwest must be repeated every 500 cycles. Southwest completed a voluntary round of checks Tuesday.