A commercial airliner is locked into orbit: that's the grabbing technical premise here, but Block (Mayday) pads it out into a sluggish melodrama. The plane is Star Streak, a luxury liner that cruises, boosted by rockets, at 3900 mph and 200,000 feet. But a nutty, vengeful engineer has sabotaged the plane--and suddenly the rocket boosters go into full power just after takeoff and don't stop until their fuel is exhausted. . . which happens only when the plane is trapped in orbit over 100 miles up where the jet engines have no oxygen to work with. So, with zero gravity, of course, all hell breaks loose among the 100 passengers; the pilots behave badly; when pretty Chris Diederich swallows a floating piece of plastic, a doctor aboard must perform an emergency tracheotomy. And there's only six or seven hours of oxygen left. Will NASA agree to send up the Space Shuttle to save them? Or will Star Streak get down by itself?. (Will it disintegrate from overheating on reentry?) A solidly suspenseful situation--with the zero-gravity mishaps suggesting some imaginative special effects. But the characters are cardboard; and the unfocused action down on earth (the search for the saboteur, the TV-network coverage, the rescue plans) sags so badly--in alternating chapters--that this soon becomes a single-gimmick thriller for astrophysics buffs only.