Complex sentence: In 1968, after Northeast Airlines began its merger with Delta Airlines and simultaneously applied to Civil Aeronautics Board to discontinue service on the Boston to Rockland route, Northeast-Delta's executives began searching for a company to sponsor as a replacement carrier.
Split into simpler sentences: In 1968, after Northeast Airlines began its merger with Delta Airlines, the new organization applied to Civil Aeronautics Board to discontinue service on the Boston to Rockland route. The Northeast-Delta's executives began searching for a company to sponsor as a replacement carrier.