My cats flew over in a Petmate Vari-Kennel with turn-locks and nobody said a word about it (I flew with BA). As long as the carrier/crate is IATA-approved, you'll be fine - shippers and airlines are MUCH more concerned with the size of the crate (and therefore how much room your pet has to move around) than the construction details. My cats are 11 and 14 pounds and I bought two of the Medium (or was it the Intermediate? I can't recall) Vari-Kennels from
this page. They look like
this.
They're a bit on the expensive side and they looked huge when I bought them, but I am REALLY glad I did - once my cats were ensconced inside with a fuzzy bed and a toy, they had enough room to stand up and stretch fully and to sleep, curled up in a ball OR stretched out from tip to tail. I couldn't imagine confining them to a space any smaller than what they ultimately spent the next eighteen or so hours in - and the crates were big enough that when we picked them up from the airport, we were able to disassemble one crate and stack the other inside in the backseat and let the boys snuggle together for the six-hour drive home.
We've currently got the crates disassembled and stacked in a cupboard here in our flat - when it comes time to take the boys into the vet for their shots next March, we'll be able to pull out two halves and reassemble one carrier and just use one instead of lugging two carriers around, and there's no way they'll ever outgrow these carriers, even if they gain ten pounds each!