Almost 100 million U.S.-operated airline flights, carrying several billion people, had taken off and landed safely over a nine-year span since the last time a passenger died in an accident in the country.

That record for avoiding fatalities ¡ª which had never been approached in the history of modern aviation ¡ª was splintered in an instant Tuesday when an engine on a Southwest Airlines Co. plane exploded mid-air, spewing shrapnel into a window and killing a passenger. The plane, a Boeing 737-700 which was bound to Dallas from New York, made an emergency landing in Philadelphia.

The death of 43-year-old Jennifer Riordan on Flight 1380 was the first in a U.S. commercial aviation accident since 2009, according to National Transportation Safety Board statistics.