Boeing 727 Prototype in the colours it first flew in.
Boeing 727 Prototype in United Airlines colours in which it flew.
The Boeing 727 was Boeings only three engined Jet Airliner. These are images of the prototype N7001U. The top picture is the aircraft in the Boeing colour that it first flew in. The bottom image is when it was in United Airlines colours.
The Boeing 727 is the featured airliner in a new bi-monthly magazine, more details at: https://www.cockpitrevolution.com/shop.html#!/Western-Jet-Airliners-Magazine-Issue-1-July-2019/p/135501118/category=0