As part of the boys pre-flight check up, the vet gave Katherine "Kitty Valium" to relax the boys during their flight. This is not a deep sedative, but something take the edge off of the scary nature of being trapped in their carriers in a noisy dark place.
The vet specifically said to test the dosage. Katherine started with a half dose a few days ago, which didn't affect them that much. They did sleep most of the dosage period (six hours), but then again those two have never exactly been insomniacs. They were relatively normal when awake.
So she upped the dose to almost a full dose. Billy most assuredly got knocked for a loop by this, he charged up the stairs at one point and a local observer worried for him. Katherine put him in a drunk tank (a cat carrier) and let him sleep it off.
So it looks a like a half dose if we use anything at all.