Phil Condit, the chairman and chief executive of Boeing, has cast further doubt on whether the US aerospace giant will go ahead with plans to launch its futuristic new airliner, the Sonic Cruiser.
Speaking to journalists at a dinner during the Farnborough Air Show, Mr Condit said: "Maybe time dims the memory but can I remind you that we have announced a lot of aircraft that we never did."
Boeing took the aviation world by surprise 15 months ago by disclosing that it was working on designs for a revolutionary new 250-seater aircraft incorporating advanced technologies. The Sonic Cruiser would operate non-stop on routes such as London to Sydney, cutting journey times by travelling at just below the speed of sound.
Since then, however, the airline industry has grown increasingly doubtful about whether the design will ever see the light of day, with Boeing's arch rival Airbus Industrie the most vocal in its scepticism.
Last month a senior Boeing executive admitted that the Sonic Cruiser team was working on a range of other designs, including a more conventional replacement for the 767, incorporating some of the proposed aircraft's technologies.
Mr Condit said Boeing would probably decide whether it was going ahead with the Sonic Cruiser towards the end of the year but denied the aircraft was a smokescreen for something else. "We are not that bright or that devious," he said. "If what comes out of the studies is a more conventional aircraft then Airbus will say 'We told you so' but that is not why we are doing it."
GKN yesterday became the first British company to join the Sonic Cruiser technology development team. GKN Aerospace has been selected by Boeing for its composite structures technology which can produce stronger, lighter air frame components capable of withstanding extreme heat.