In atmosphere, perhaps.
In space they'd quickly die as the gas in their bodies (oxygen/nitrogen) rapidly expands and forms bubbles, boils away, and turns them into an agonizing hideous and bloody mess. No kidding. They'd be dead long before asphyxiation had a chance to set in. And no, despite popular miconception, people's bodies don't explode in a vacuum - it'd probably be a quicker and less painful death if they did, though. This is essentially what happens to deep sea divers who surface too quickly, though on a much more extreme end of the spectrum.
The entire flight suit would have to be completely sealed and pressurized in order to survive if the cockpit depressurized in space.
Oooh, brings back memories of Event Horizon.