But nobody has really answered the question of WHY United does this. Does anybody know the advantage of having one flight number for a series of flights using different types of aircraft? Is it to conserve flight numbers. What does United call it if you have a change of plane but it's the same type of plane -- i.e. UA #1 from JFK-LAX on one 747-400 and then the next segment of the flight is on another 747-400 -- not that this ever happens.