Daniels-

Welcome to Flyertalk. You should know that CO’s transcon flights in coach are the most uncomfortable way to fly ever invented. They use all narrow body aircraft, mostly 737s with an occasional 757. Seat pitch is terrible – you will be sucking your kneecaps for 5 hours. With the small planes, there aren’t as many first class seats to upgrade to. In short, UA or AA is much better.