It seems fair to ask a university to use the largest, safest planes available. It seems more than fair to ask a school to keep the team together. Most schools do this. Most schools have it easier than the Big 12 conference. East Coast universities are usually close enough to major airports to fly commercial, or at least land decent-sized charter jets.
Smaller schools get by with buses.
Schools such as OSU and Texas Tech are burdened by location. Small-town airports can't always accommodate big planes. Commercial flights are limited. Even so, only a few Big 12 basketball programs use prop planes to travel. The rest manage to find chartered jets with at least 30 seats, enough to keep the team and its critical personnel together.