Originally Posted by
ft101
Nobody can be definitive. If yours are too big and you take them then you run the risk of them being taken from you and being charged to put them in the hold. Anecdotal stories of others getting away with it won't help you. If you have to buy suitable bags, there would be no reason to discard them after the trip.
Ryanair sized bags would be too small for US carriers (and also, technically, too wide in one dimension - although no one checks here). Since the trip is for 3 people, that means 3 bags that are too small to be useful for most of our travel, while tripling the price of the tickets (that and my bag collection is getting pretty extensive, something will need to be discarded).
FWIW our carryons traveled on Ryanair last year, but it was just one flight and I am not sure how representative that was.