Thanks to everyone who made suggestions. I looked at the Pro-Pet web
site, but did not think the concept was very appealing. The cost is
about the same as a round-trip airline ticket. I don't doubt that they
give the animals good care, but a 2000-mile road trip sounds a lot
more stressful for a cat than a trip in an airplane.

They seem to cater to people who like to pretend that their cats are
little people. "Send your cat's favorite video so they can share it
with their new friends"? I'd like to show them a video of my cat's
reaction when a "new friend" approached the partly-open patio door
last week!

Companion Air looks like an ideal solution, although it is indeed very
expensive. But it clearly won't be ready in time for my trip next
month.

To answer some of the questions: some airlines allow two cats in one
carrier, but not fully grown cats. That's entirely reasonable; a
carrier large enough for two grown cats would not fit under a seat.

I may drive, although I will try to avoid it; I have a tight schedule
(and tight finances). But I would not dream of driving two cats 2000
miles in a car. (And no, I do not allow either cat to drive.) Renting
a motorhome would provide a half-way comfortable environment, but it
would be frightfully expensive, would take at least as long as driving
a car, and would leave me with the trouble and expense of transporting
my own car.

I'm probably going to recruit another traveler to carry my second cat
on the plane and pay half of his or her fare in exchange.

My mail address is jsachs177 at earthlink dot net.