Not being funny, I thought the B748 was the world's longest airliner?
A340-600 was the longest for a while, until the 748 entered service:
747-400: 70.6m
777-300ER: 73.9m
A340-600: 75.36m
747-8i: 76.3m
Although technically the An225 is the longest, at 84m.