Advice for airline flying with dog

I’m going to be traveling from Boston to San Diego (probably with a layover, so my dog can pee and stretch). I am moving for summer employment.

Last time I tried to fly with him, we were told that he was too big to be in the cabin. He’s 14 lbs, and fit in the carrier, but he couldn’t stand up and spin around without touching the sides of the crate.

Does anyone have advice for which airlines will be less strict about this?