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 centrepiece of this "Haynes Manual" is the 747-400, which is the most numerous version. As well as being the highest-selling model in the 747 family, there are more 400s currently in service than any other version.