Both the 757 and the 767 have roots going back to the early 1970s. The 757 was developed as an advanced version of the single-aisle 727 and was manufactured at Boeing's Renton Facility, while the 767 was developed as a twin-aisle jet and Boeing's Everett facility was expanded to accommodate 767 production. Much effort was made to obtain the maximum level of common training and parts interchangeability between the two aircraft.