car travel is FAR preferable for the cat. Your Sherpa bag will fit under a
plane seat....but the noise is deafening & very traumatic for the cat. You are
right not to tranquilize. In case of turbulence, the cat has to be able to
brace itself.
4-6 hours in a car is nothing. And along the route you can talk to the cat,
comfort it, supply treats & water. Worst case scenario, you can put on a leash
& let the cat use a sandbox....but probably the cat will 'hold it' out of sheer
terror anyway. For the same reason, it might not want food or water. But, nice
if they're available.
Besides, airlines (and only a few of them) - as of 6 years ago- only allowed 3
animals per cabin, so reservations had to be made well in advance.
Under no circumstances should a pet ever fly as cargo. Especially a cat like a
Persian that already has breathing difficulties.
My two cents!