President Reagan won't get to ride on a new Air Force One before he leaves office because the airplane's contractor is months behind schedule with no prospect of making up the delay, Air Force and company officials say.

The Boeing Co., which is building the new Air Force One and a back-up plane by customizing huge 747 passenger jet airframes, "advised us last week they won't be prepared even to finalize a new delivery schedule until mid-to-late October," Lt. Col. Darrel C. Hayes, an Air Force spokesman, said Monday."So, obviously, delivery won't occur in November as anticipated but rather next year," Hayes continued. "And the delivery is going to occur later in the year, probably summer, and not in January (before Reagan steps down)."

Boeing's contract with the Air Force called for delivery of the first plane by Nov. 30. Three months ago, however, Air Force officials disclosed Boeing was going to miss that deadline because of problems with installing wiring for the plane's specialized communications gear.

At the time, James C. McKinney, the chief of the White House's military office, said he still was hopeful the company could get the first plane delivered by Jan. 20 - Inauguration Day - to enable Reagan to take a ride on the new plane as he began his retirement to California.