The crash comes after a remarkable period of safety for airlines in the United States. It has been four and a half years since the last airline crash — a safety record unmatched for half a century. That accident involved Colgan Air Flight 3407 (operating as Continental Connection Flight 3407), which crashed on approach to Buffalo International Airport, killing 50 people, including one on the ground on Feb. 12, 2009. Globally, as well, last year was the safest since 1945, with 23 deadly accidents and 475 fatalities, according to the Aviation Safety Network, an accident researcher.