What the Peeper Saw AKA Night Hair Child
(1972, Britt Ekland, Mark Lester, Hardy Kruger)
A thriller most notable for its depiction of an inappropriate relationship between a young boy and his stepmother (Lester and Ekland) but opens with an evening view of an airliner approaching Heathrow over a group of BEA AEC Routemasters, one of which passes the camera towing a trailer: