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Investigators were not ready to dismiss the possibility that Flight 811 was the target of a terrorist bombing, especially when it was recalled that in January a Honolulu radio station received a call from a man threatening to plant a bomb on a U.S. plane unless a member of the Japanese Red Army was released from a U.S. jail. The immediate speculation, however, was that a cargo door had simply been whipped off in flight, taking a large portion of the fuselage with it. If that was the case, the incident was one more in a series of mishaps in which commercial aircraft have lost huge sections of their fuselage in midair. Last April a flight attendant was killed and 61 people were injured when a sizable piece of the fuselage of a Boeing 737 peeled off on an Aloha Airlines flight from Hilo, on Hawaii Island, to Honolulu, on Oahu. A subsequent inspection of all 737s ordered by the Federal Aviation Administration turned up tiny stress cracks in nearly half the planes. In December an Eastern Airlines Boeing 727 was forced to land in Charleston, W. Va., after a 14-in. hole blew open in the plane's body.
The tragedy of Flight 811 was a further setback for Boeing, which in recent weeks had to acknowledge that some of its new planes were rolled out of the factory with faulty -- and potentially dangerous -- electrical wiring. In today's atmosphere of rough competition fostered by airline deregulation, a number of U.S. carriers have been accused of pushing their aging fleets to the limit and disregarding manufacturers' maintenance recommendations.
At the same time, individual planes are making more flights and longer ones. A chief measure of wear and tear in an aircraft fuselage is the "pressurization cycle" -- one takeoff, one landing -- which requires that the cabin be pressurized for high-altitude flight and then depressurized during descent. This places stress on the airframe; over time, repeated expansion and contraction weaken the plane. Like a balloon that has been inflated too many times, the plane's skin becomes vulnerable to tearing. But while the Flight 811 jet has been in service for 19 years and is one of the oldest in United's fleet, it had racked up only 15,021 cycles, considered middle-aged for a 747 but not dangerous.
This week the Air Transport Association, the airlines' trade group, is expected to recommend some 200 changes in federal regulations that govern maintenance. One especially significant proposal: to remove airliners from service after a specified level of wear and tear, perhaps 80,000 cycles, and rebuild the planes from the wheels up. Says A.T.A. Vice President William Jackman: "It's a first step in a series of safety measures . . . a major effort by the airlines and planemakers to assure the airworthiness of passenger aircraft." With planes falling to pieces in the sky, passengers will appreciate that.