Traveling with cats

I am about to relocate from the east coast to the west coast. I'm taking my two 2.5-y-o cats onboard, to fit underneath the seats in front of me and my companion (already arranged with the airline) in soft-sided carriers in which they can lie down but not really sit up. My cats have never gone anywhere farther than the vet a few miles away, and this will be a long trip.

Any recommendations for minimizing the stress to my 2 cats? I'm worried about their stress in the plane, pressurization issues, providing water for them, being cramped for many hours, and having no litter box during the flight.

[tina1111]

I traveled from Washington State to Florida with my cat. The vet gave me some tranquilizers to keep him asleep to minimize the stress and confinement. He did great. If he were awake and in that tiny carrier, he would have howled until they made a landing to put him in storage, lol. I had to re-med him 1/2 way through the trip.