Is It Safe To Fly In Older Planes?

The mid-air incident in which a hole opened in the roof of a Southwest Airlines Boeing 737 has some travelers wondering what type of aircraft they should be flying, and how old is too old.

The plane in question landed safely and inspectors attributed the rip in the fuselage to tiny cracks. Southwest, which exclusively flies the Boeing 737, immediately launched an inspection and subsequently reported finding similar cracks in five other jets.

The Boeing 737 is an old aircraft type, entering service in 1967. However, Southwest’s jets aren’t nearly that old. Southwest flies the 737-300, which began to enter the fleet in the 1980s, with the 400 and 500 series following in the 1990s. Although the 737 is an old aircraft type, not all of the planes in service are old, since the manufacturer is still turning out 737s.

Commercial aircraft are expensive, highly maintained machines that can operate for decades. Engines are replaced and electronic systems are updated. Even 30-year-old jets are nearly as modern as the latest additions to the fleet.

Tiny stress cracks

The problem maintenance crews must watch for, however, is the appearance of tiny stress cracks in the skin of the airplane. During each flight the cabin is pressurized and depressurized, causing stress to the fuselage. Over time this constant stress can wear on the body of the plane, causing metal fatigue.

A spokesman for Boeing is quoted in the media as saying the 737-300 is not expected to show any signs of stress until after 60,000 take-offs and landings. According to the website AirSafe.com, the jetliner involved in last week’s incident had about 40,000.

The cracks causing last week’s incident were so small they would not have been detected with a visual inspection. However, at the time, a visual inspection was all that was required. That has now changed.

New inspection procedures

This week Boeing issued a service bulletin detailing an updated inspection procedure that could detect stress crack problems on the 737 300, 400, and 500 series planes. The Federal Aviation Administration (FAS) issued an Airworthiness Directive requiring these advanced inspections on all affected aircraft within 20 days, and within five days if the aircraft has logged more than 35,000 take-offs and landings.

Going forward, aircraft with more 30,000 take-offs and landings, which are called “flight cycles,” must have the new inspection procedure repeated every 500 cycles. These new procedures, says AirSafe.com founder Dr. Todd Curtiss, reduce the risk for the average passenger.

Southwest experienced a similar fuselage rip in 2009 on a Nashville to Baltimore flight. Unlike last week’s incident, the tear occurred in a different area of the airplane.