Earlier this year, Boeing was also selected by the Pentagon's Defense Advanced Research Projects Agency (DARPA) to develop the XS-1 space plane that would be "the first of an entirely new class of hypersonic aircraft" that would provide "short-notice, low-cost access to space", DARPA stated.
Others believe the secret plane could be a new electric aircraft with a hairdryer-type engine allowing it to take-off and land vertically.
The speculation follows Boeing's recent acquisition of the Aurora Flight Sciences, which last year won a contract to build the XV-24A LightningStrike VTOL (Vertical Take-Off and Landing) plane for the DARPA design competition. Aurora has reportedly been developing electric-powered aircraft for long-haul flights for both commerical and military purposes.
The XV-24A aircraft will be the first in history to demonstrate a series of unique features including the distribution of "hybrid-electric propulsion ducted fans" and an "innovative synchronous electric-drive system".
This new VTOL plane would reportedly increase the aircraft's hover efficiency to 70 per cent, from 60 per cent and allow it to carry a load of at least 40 per cent of its projected gross weight of 10,000-12,000 pounds.
But the structure of this ducted fan technology doesn't match the silhouette of the mystery aircraft revealed by Boeing, as noted by The Drive.
The new plane could also be a version of the Phantom Swift, Boeing's own VTOL aircraft which was originally submitted as a proposal for the competition that Aurora won.