Thank you all for your support and suggestions. I will FedEx the pet bag to Tucson with a nice ripe, smelly, stinky tee shirt I made my hubby wear for three days.

The foster mommy will leave it in the x-pen when she goes out and put toys and treats in it. When she is home, she will put him in it for short periods and even take him for a ride in the car so he gets used to engine noise and vibrations.
I am still worried about the outcome.

I hope my hubby is not stranded at the airport with Yogi, unable to fly, and the foster mom is long gone. She needs him out of her house by the 13th, and I don't even know if she would take him back or hang around to find out if they were both able to board the plane. Talk about being between a rock and a hard place!
Sookie, I give you credit. What a nightmare! I am so grateful we are not flying that airline. How stupid of them to make you stuff a tiny baby into what amounts to a matchbox, especially when your carrier would have fit just fine. Where do they find these morons? I used to have migraines complete with vomiting so I know how miserable and embarrassed you must have been.
I was wondering if those of you who have flown would mind telling me which airline you used? Also, has anyone tried to fly with a dog out of Tucson?
Thanks again everyone. I am grateful for your help. If Den wasn't in the middle of a job search, we could have taken a week and had a nice leisurely drive out and back, with several days spent there to bond with Yogi. Unfortunately, Den must stay here so he can be available for interviews--they don't give you much notice, and if you're not available when they have a time slot, they just go to the next person on their list. That's why he's doing the out-and-back thing on a Saturday, and a particular health problem I'm having right now requires me to stay close to home.
If I had known about the Yorkie Train, it might have been a better solution, considering the relatively short distance (a 14-hour drive between Tuscon and Dallas according to Map Quest) and Yogi's larger-than-average Yorkie dimensions, and I could have paid it forward after I recover from my surgery in September. So close, but so far. I will be a wreck until I see them both come through the front door.
Thank you all for your help.
Sandy
P.S. I've attached some photos of Yogi. He sure is a handsome little man.