Many thanks John, confirmed my suspicions. Nervous about an acoustic guitar in a gig bag (which seems the surest way of being allowed a guitar on board) in the overhead locker. I see the way the lockers get packed and the contents abused by passengers trying to cram maximum luggage into an already full locker.
Guess I will stick to the hard case in the hold and keep my fingers crossed. No problems with damage so far, only loss for up to 11 days and that was due to the Heathrow terminal 5 opening fiasco.
Almost embarrassed to admit I have three Avalons now (acquired over a No of years)I first bought an A325c Auditorium and then wanted a jumbo and seen a L25C ex demo on the Avalon website, and yes I bought it. I justified buying one more on the basis that I spend a lot of time in Norway where I have a company flat. I took the A325C to Norway and replaced it with a L320C Jumbo with added justification (this was the sales pitch to my wife) that I need to explore the tonal qualities of the two different woods used for construction.
All guitars provide phenomenal projection and sound quality, build quality on all three are exquisite and interestingly I don't notice the diffence in body size moving from auditorium to jumbo.
Once again many thanks for the links.