Probably Lorazepam from the vet...anti-anxiety drug. We used to take cats on planes to Canada...I covered their carriers with cloth, mostly to keep people who freak out at cats from seeing them, but I think it also helped the cats.
Yeah my wife took her white persian with us on a start up I was on in Montreal. Well, the cat wound up in Nova Scotia. This took us three days to figure out and another 2 to get the cat to Montreal. Well, the apartment my company leased was completely white, bright white. Furniture, fixtures, everything except for the TV.
Well when this stressed out cat got there and we finally let it out of the crate, it went nuts and started running around and bumping into all the white furniture against the white walls and fell over, passed out or knocked out. About an hour or so later, it popped up squalled and finally made it thru a door and under a bed, where it stayed for the better part of a day.
The cat was never the same and would spaz out at the drop of a hat. I think something in its brain broke.