When the seats shudder and the wings flutter and the engines crescendo in what sounds like a last and mighty effort to lift off, what traveler has not wondered nervously whether the plane should be retired? America's aging fleet of passenger jets became a national concern last April when a 19-year-old Aloha Airlines 737 ripped apart in midair. Since then, cracks have been found in the fuselage of some of the other 429 Boeing 737-100s and 737-200s still flying in the U.S., giving rise to fears that regular inspections are not enough to ensure safe flights.
Last week the Federal Aviation...