CHICAGO (AP) -- Here's proof. Consumers are fed up with the airlines.

An annual survey released by the University of Michigan finds customers giving airlines the worst grades since 2001. The industry's overall scores are down for a third straight year.

United Airlines and US Airways Group, which are in talks to potentially combine into a single carrier, finished next-to-last and last, respectively, in the university's American Customer Satisfaction Index.

Continental Airlines and US Airways registered the biggest declines from 2007, both experiencing double-digit percentage drops.

A familiar bright spot in the results was Southwest Airlines, which led the industry in passenger satisfaction for the 15th consecutive year.