Original sentence: Since Boeing sold the first sixty off the production line to its affiliated airline (Boeing Air Transport), TWA (Transcontinental & Western Air) then tasked and funded Donald Douglas, Sr
Edited sentence: In later years, with the 707 and other jets, Boeing always made sure that first year deliveries were spread between several airlines.Shutting out TWA led to the DC-3 development.Since Boeing sold the first sixty off the production line to its affiliated airline (Boeing Air Transport), other airlines were stuck with fleets of planes that passengers didn't want to fly on.TWA (Transcontinental & Western Air) then tasked and funded Donald Douglas, Sr.The 247 rendered all other aircraft obsolete.The delivery of the first 60 247's to BAT was Boeing's big mistake