SpaceShipII is expected to take passengers to an altitude of 68.3 miles in just a two-hour flight that includes a four-minute period of weightlessness.

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Just as airlines require passengers to turn off their mobile devices for the duration of the flight, the withdrawal is confined to a limited period.

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My wife and I flew to Argentina in 1995 after a long period when neither of us had taken a long-haul flight for many years.

BBC: News Online

He found that the aircrew given the shorter period to "turn around" after a jet-lagging flight had an area of the brain called the temporal lobe which was noticeably smaller than the others.

BBC: stewardess

The FBI then approved -- after some period of time, and I can't tell you how long -- approved the flight.

CENTERFORSECURITYPOLICY: Center For Security Policy

If there can't be a new manned mission from Earth by then, administrators will have to decide whether to take extensive steps to extend the vehicle's certification for the return flight, proceed on a return flight without certification, or de-man the space station by flying back the remaining crew members within the certification period, he said.

CNN: Russia postpones new manned space station mission