First introduced in West Germany as a short-hop commuter jet in the early Cold War, the Boeing 737-100 had folding metal stairs attached to the fuselage that passengers climbed to board before airports had jetways. Ground crews hand-lifted heavy luggage into the cargo holds in those days, long before motorized belt loaders were widely available.
That low-to-the-ground design was a plus in 1968, but it has proved to be a constraint that engineers modernizing the 737 have had to work around ever since. The compromises required to push forward a more fuel-efficient version of the plane — with larger engines and altered aerodynamics — led to the complex flight control software system that is now under investigation in two fatal crashes over the last five months.
Boeing's problems deepened Thursday, when the company announced it was stopping delivery of the aircraft after the Federal Aviation Administration's decision Wednesday to ground the aircraft.