That's the finding of the Airline Quality Rating, a report issued each year by professors from Purdue University and Wichita State Univeristy.
Part of what contributed to United's poor ranking is that it had the second highest rate of customer complaints.
The report found that Delta had the highest rate of complaints of all the airlines surveyed.
American Eagle was rated the meanest regional carrier and the one most likely to bump passengers.
The airline that was most likely to be late was Comair.
The report found that only about 73 percent of Comair flights arrived on time.