A new bullet-shaped aircraft that massively reduces the cost of flying is the "the biggest thing to happen to both the aviation and travel industries in 50 years" according to its manufacturer.
Aviation enthusiasts first spotted the Celera 500L from Otto Aviation flying over California in 2017. Immediately questions were raised over where this unusual-looking aircraft came from and who built it.
Now Otto Aviation has finally gone public with the details on a new website. Far from the speculative designs we sometimes see for future supersonic jets and other aircraft, the Celera 500L has already completed 31 test flights with the full-scale prototype.
Otto Aviation claims it is the "most fuel-efficient commercially viable passenger aircraft in the world".
The plane, which can carry up to six passengers, is designed to compete with commercial aircraft by providing chartered flights at a cost that's comparable to flying with a regular airline.
"Our goal was to create a private aircraft that would allow for direct flights between any city pair in the US at speeds and cost comparable to commercial air travel," said William Otto, the company's chairman and chief scientist.
"In many cases, individuals and families will be able to charter the Celera 500L at prices comparable to commercial airfares, but with the added convenience of private aviation."
The Celera 500L has a maximum cruise speed of 724 km/h and a range of over 7240 kilometres. While this doesn't put it in the league of top-tier, long haul private jets, which can do as many as 13,000 kms and travel at close-to the speed of sound, the Celera 500L is designed for shorter hauls between regional airports, avoiding major hubs.
Watch: The Celera 500L in flight
The range would allow the plane to easily complete any domestic route within Australia, with potential for flights to south-east Asia and the Pacific.
Inside, the aircraft promises six "first class" seats and significant headroom for a small plane, with a cabin height of 1.88 metres. The current prototype has no passenger windows, but Otto Aviation says this will change for the passenger version of the aircraft, as shown in renderings.
But the big selling point is the fuel efficiency and operating cost. The plane can do between 7.7 and 10.6 kilometres per litre, compared with 0.7 and 1.3 kilometres pe litre for similar sized planes.
The Celera 500L has an operating cost of $US328 ($A446) per hour, which is far lower than typical private jet costs, which typically cost at least $US1000 and as much as $3000 per hour.
The key to the aircraft's efficiency is its aerodynamic, bullet-like design, which maximises the smooth flow of air over the fuselage, wings, and tail surfaces.
It also greatly reduces emissions, with Otto Aviation claiming carbon emissions are 80 per cent lower than comparable private aircraft and 40 per cent lower than modern commercial planes. The plane already surpasses the US Federal Aviation Administration's 2031 emissions standards for new aircraft by more than 30 per cent, Otto Aviation says.
The company is currently arranging a second-round of funding for the design and still needs to begin the FAA certification process. All going to plan, Otto Aviation aims to start delivering the Celera 500L to customers between 2023 and 2025.