Amazon's billionaire founder Jeff Bezos says he and his brother Mark will fly on the first crewed space flight from his rocket company Blue Origin next month.

The highest bid for a seat on the space flight was $US2.8 million ($3.6 million).

Mr Bezos, who is due to step down as Amazon's chief on July 5, will join the winner of an auction for a seat on the first space flight from Blue Origin.

Mr Bezos, fellow billionaires Elon Musk and Richard Branson have been investing billions of dollars on their rocket startups, but Mr Bezos will be the first of the three to actually travel into space on a rocket developed by his own company.

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The Blue Origin spacecraft, which is set to carry Mr Bezos and others, has undergone 15 test flights, none of which had any passengers onboard.

Its New Shepard rocket-and-capsule combo is designed to autonomously fly six passengers more than 62 miles (100 km) above Earth into suborbital space, high enough to experience a few minutes of weightlessness and see the curvature of the planet before the pressurised capsule returns to earth under parachutes.

The capsule features six observation windows and are nearly three times as tall as those on a Boeing 747 and the largest ever used in space.

Mr Bezos's rocket startup is targeting July 20 for its first suborbital sightseeing trip, a landmark moment in a competition to usher in a new era of private commercial space travel.

Reuters