Back in 1987 when we brought our Yorkies and Lhasas into the USA from England we had to bring them cargo. Was a long flight, but they were fine.
Only complaint was that when we arrived in Atlanta, we had to pick them up with the baggage at the baggage claim area - they were on the conveyer belt with all the luggage!!! They were just going around the conveyer belt in their separate cages. I thought at the time that just anyone could have picked them up!
And although we went through all the procedures of getting the vet OK papers which we were told we would need, no-one asked to see them.
But that was from England to the USA.
But cargo was fine