Among the aerospace luminaries gathered in Paul Allen's Seattle aerie for the announcement of his giant space cargo plane was his friend and former co-worker Charles Simonyi.

Simonyi reported to Allen in the early days at Microsoft, when Simonyi was developing the company's productivity suite, and the two shared a passion for space travel.

On a last minute whim, they traveled to Florida together to watch the launch of the first space shuttle in 1981.

They weren't going to make it because the launch was scheduled for a Friday -- the same day as Microsoft's first big company meeting.

But a software glitch delayed the launch until a Sunday, so Simonyi and Allen decided to go after the meeting and made the historic takeoff.

Allen was also on hand when Simonyi made history as the first space tourist to make a repeat flight to the International Space Station, in 2009, and traveled to the launch in Kazakhstan.

The two Microsoft billionaires also share an interest in airplanes and boats, and own some of the largest yachts in the world.

At Tuesday's announcement in Allen's glass-walled penthouse offices above Seattle's Union Station, Simonyi lauded Allen's plans to build an enormous airplane to ferry space cargo into orbit.

"I think it's audacious and doable," Simonyi said.

"It's a fantastic team -- they all know what they're doing."

Simonyi said he's not going to invest in the venture but he might ride in the craft someday.

"Once proven and, if my wife lets me, yes," he said.

Simonyi said space travel is going through the same evolution as aviation -- from experimentation to military development, followed by barnstorming and then the rise of commercial service.

As the industry progressed, flight became more accessible and people no longer have to wear parachutes when traveling, he noted.

The same thing should happen with commercial space flight, he explained, so you eventually won't need the bulky space suits and intensive training that was required for him to travel on a Russian spacecraft based on 1960s technology.