Business Notes AEROSPACE

Morton Thiokol, the company that built the booster rockets for the space shuttle Challenger, has decided to retreat from its long and painful association with the shuttle program. Last week the Chicago-based aerospace and chemical firm said it would decline to bid for the $1.5 billion NASA contract to build motors for the shuttle's next generation of solid-fuel boosters.

Thiokol's stated rationale is to concentrate on correcting flaws in the current booster model, which will be phased out starting in 1994. Company officials may also have concluded that Congress would be reluctant to award another contract to a company that was partly to blame for the 1986 explosion that killed seven passengers.