Complex sentence: Seaboard World Airlines Flight 253A was a military charter flight carrying 214 American troops on bound for Vietnam, that on July 1,1968, was intercepted by Soviet jets and forced to land on Soviet territory because it had unintentionally violated Soviet airspace.
Split into simpler sentences: Seaboard World Airlines Flight 253A was a military charter flight carrying 214 American troops bound for Vietnam. On July 1,1968, the plane was intercepted by Soviet jets after it unintentionally violated Soviet airspace.