When the Boeing 747 first flew commercially in 1970, it ushered in a new era of affordable air travel. Often referred to by the nickname “Jumbo Jet,� the 747 was the world’s first wide-body commercial airliner, and its advent has proved to be one of the major milestones in aviation history. The centerpiece of this Haynes Manual is the 747-400, which is the most numerous version. As well as being the bestselling model in the 747 family, there are more 400s currently in service than any other model of this mighty jumbo.