Tom Enders just couldn't resist the swipe at the competition. It was June 2011, and the chief executive officer of Airbus SE was on a stage at the Paris air show after the plane-maker won in a matter of days an unprecedented 600 orders for its upgraded A320neo airliner, while Boeing Co. stood on the sidelines.

"If our colleagues in Seattle still maintain we're only catching up with their 737, I must ask myself what these guys are smoking," Enders blurted out, to the general amusement of the audience, while Boeing representatives at the back of the room looked on.

Boeing had wavered on its decision whether to follow Airbus's lead and re-engine the 737 or go with an all-new aircraft. Customers were willing to wait for "something more revolutionary," as Jim Albaugh, at the time Boeing's head of commercial aircraft, said then.