Another +1. The A380 is much larger than what USA airlines want to run on domestic routes. The A319/20/21 are more in the sweet spot. Even for overseas flights the A380 is too big. It's roughly twice the size of the B747. Where traffic demands more than a 747, they'd rather operate 2 smaller flights daily with different departure times than a big, once-a-day A380 flight. The B787 is a better fit, slotting in between the 777 and 747 in size. Of course, all the USA based airlines with major international operations are in poor financial shape right now, so they're not rushing to take delivery of new aircraft or significantly revamp their offerings.