Every de Havilland Comet airliner made in Hatfield had to be tipped tail-down when advancing it along the Final Assembly line as the roof clearance height of the pre-war building was too low for its 29'6" top of fin height. Being a north-light roof the fin could go in between the structure when the next staion was reached. For the Trident a High Bay was added to the end of the shop as they couldn't do the same trick once the tailplane was fitted.