WASHINGTON (AFP) - Seeking to cash in on the space tourism boom, a US firm is offering rides in a helium balloon 30km up to gaze down on Earth.

The Arizona-based company World View Enterprises said in a statement on Tuesday the trip will cost US$75,000 (S$92,720) and travellers will stay aloft for about two hours in an eight-seat "luxuriously appointed space-qualified capsule".

The capsule will ultimately detach from the balloon and glide to the earth with a parachute.

The flights are scheduled to start in three years.

"Passengers will be among the few to have seen the curvature of the Earth with their own eyes," the statement said.

"They will be able to gaze at the astounding views, the blackness of space, the brilliance of stars and the thin veil of atmosphere enveloping our planet - scenes previously witnessed exclusively by astronauts - for US$75,000," it added.

"Seeing the Earth hanging in the ink-black void of space will help people realise our connection to our home planet and to the universe around us, and will surely offer a transformative experience to our customers," said Jane Poynter, CEO of World View.

She is also the co-founder of Paragon Space Development Corporation, which developed the capsule and brought together investors to create the balloon flight venture.

The Federal Aviation Administration has classified the World View capsule as a spacecraft, according to an FAA letter published on Tuesday by the company.

Technically, space begins at an altitude of 100km. From there on up, aerodynamic flight is no longer possible because there is no atmosphere.

Virgin Galactic, created by British billionaire Richard Branson, plans flights to that sub-orbital altitude starting in 2014.

Virgin Galactic has already sold nearly 650 tickets. The price has gone from an original US$200,000 to US$250,000.

Paragon is working with multi-millionaire Dennis Tito, the world's first space tourist, in 2001. He plans a 500-day round-trip journey around Mars with two astronauts.