- "Marty looked out the window. Wherever they were, the floating lane markers [of the skyway] were gone. It was night, and all he could see were tiny lights below. / 'Did we make it?' Marty asked. / As if in answer, a 747 jumbo jet roared much too close overhead. The DeLorean shook violently for a moment before Doc stabilized it again. / 'We're back,' Doc agreed. 'Now let's get Jennifer home.' "
- —From Back to the Future Part II by Craig Shaw Gardner (quote, page 96)
An airliner was a large passenger aircraft.
When Doc, Marty, Jennifer and Einstein returned in the hover-converted DeLorean time machine from 2015 back to what was believed to be 1985, but was actually a nightmarish alternate reality, the DeLorean's altitude was slightly below the flight path of a descending commercial airliner and there was very nearly a midair collision.
Whether the aircraft in question belonged to an airline owned by Biff Tannen in this timeline remains unrecorded.
Behind the scenes
- The airliner is identified as being "a 747 jumbo jet" — or Boeing 747, to give it its proper name — in the novelization (see Quote above).