In May of 1952 the British aircraft manufacturer, deHavilland, delivered the first Comet aircraft (shown below is a Comet 4, introduced in 1958). The Comet was the world's first commercial jetliner. With a cruising speed of 490 mph at altitudes up to 40,000 ft, introduction of the Comet was a significant milestone in the aircraft industry. Exactly one year after its introduction, a Comet broke up in flight near Calcutta, India. In January, 1954, another Comet fell into the sea near Elba. Three months later, a third Comet crashed near Naples, Italy.  The Royal Aircraft Establishment at Farnsborough, England conducted an investigation into the cause of these crashes.  Although the exact cause will never be known, it is generally agreed that failure was initiated at a stress concentration at the corner of a window.  It should be noted that at the time, Great Britain dominated the aircraft manufacturing industry. Problems with the Comet provided an opportunity for American airline manufacturers to enter, and eventually dominate, the market for commercial aircraft.  In the MCE301 case study, students performed a finite element stress analysis of the stress concentration at the corner of an airplane window using the commericial software, AlgorŪ.  In the analysis, the effect of the window geometry on the stress concentration was explored.  Shown below is a typical stress contour plot showing the stress concentration at the corner of the window.