American Airlines Inc., the largest U.S. carrier, is expected to order up to 160 McDonnell Douglas Corp. jetliners worth more than $7 billion as part of an aggressive expansion plan, airline officials and analysts said Friday.

The Fort Worth, Texas-based carrier, a unit of AMR Corp., will announce the order for 60 MD-11 long-range aircraft and up to 100 MD-80 medium-range planes at a news conference set for Tuesday here, the sources said. It would be the second largest jet aircraft order in history.An American spokesman confirmed a news conference will be held Tuesday but declined to say what it was about. McDonnell Douglas spokesmen refused to comment.