Complex sentence: There are long-standing conspiracy theories about the cancellation of the Flying Wing program; specifically, an accusation from Jack Northrop that Secretary of the Air Force Stuart Symington attempted to coerce him to merge his company with the Atlas Corporation-controlled Convair.
Split into simpler sentences: There are long-standing conspiracy theories about the cancellation of the Flying Wing program. Specifically, there is a long-standing accusation from Jack Northrop that Secretary of the Air Force Stuart Symington attempted to coerce him to merge his company with the Atlas-Corporation-controlled Convair.