I flew from San Francisco to Philadelphia (5 1/2 hr flight) with Lito under the seat in front of me. He is 16 lbs so it was a somewhat snug fit even with the large sherpa! I think your flight from NY to CA would be about the same amount of time right?
Here were a few things I noticed: 1) The whole peeing situation. If you add in the hour minimum before the flight that you have to be ready to board + the time it takes to disembark, you are at about 7 hrs, so unless you can get the pup to pee on a pee pad (I tried with Lito and even though he uses them everyday at home he was resistant in the bathroom, I think he had stage fright
) it can be long on the dog to go without peeing.
2) I checked and re-checked the dimensions under the seats (I flew US Air) via the airline website and over the phone, but my sherpa bag BARELY fit underneath, and I had to move my seat from the window since it didn't fit under that seat due to the curvature of the plane. It almost didn't fit, and 1 stuardess who was a real (rhymes with witch) and clearly didn't like dogs tried to call the pilot and tell him it didn't fit under the seat, even though the bag was rated for their airline AND it fit in the "sample carry-on measurer" in the check-in line. 2 of the stewardesses were so nice and kept letting me poke Lito's head out for water or to pet him (we were in the very last row near the bathroom so no one could see us) but the same witchy one kept making me duck his little head back in. She must've been PMSing
But I have to say Lito was the perfect flier, he didn't make a single sound the whole time, he was such a good boy and I was so proud of him!
So I guess it will depend on the airline and how strict the stewardesses are. You won't have the size issue with a puppy (you can use a medium sherpa) so he should fit perfectly, but if you get 1 mean stewardess then he has to stay hidden the whole time, which may be fine if he sleeps but if he is restless could make it harder.
I also paid 80$ one way and had to have paperwork proof from the vet that he had his rabies shot (though they never checked it).
The funny part was that while that one stewardess was watching us like a hawk, there were two children running up and down the aisles screaming and she didn't say "boo" to them!!!!!!!
I am sure it will all work out! Can't wait to hear what you decide.