I had a smilar problem last year when my wife and I flew out to Australia. I rang AMEX first
before buying the tickets to confirm that the transaction would not be declined. I explained
to her that we had the money in the bank and that the account would be paid in full, as usual.
The woman explained to me that it would not even though we were going over our credit limit
by about £2,000. She did, however, point out that we would be charged a fee for going over
our limit. I remember telling her, "Yeah, considering how much we are spending, I doubt the
fee will break the bank." She just laughed
Perhaps it may be worth to seek a similar clarification before you buy. Either that, spread out
the flights over the billing cycles.
H