Airport lines.
Credit: Paul J. Richards/Getty Images

Even though a record 51 million passengers will fly on U.S. airlines this holiday season, a whole lot of them aren't happy about it.

Many American travelers think the flying experience has gotten worse, according to a Morning Consult/U.S. Travel Association survey released Wednesday. Their biggest complaints: more airline fees, the cost of flying generally, and airport inconveniences.

Compared to five years ago, 60 percent of respondents said fees for checked bags, flight changes, and seat assignments are worse now, 51 percent said “the overall cost of flying” is worse, and 47 percent complained of long lines and crowds at airports.

Respondents identified Christmas as the holiday when air travel hassles are the worst.

The survey, which highlights growing passenger frustration, is something of a contrast to industry data, which shows airfares staying flat in price and relatively cheap.

However, fare data does not fully represent the extra fees that have become so common. Since so many services that were previously included in a base fare now incur charges, travelers are likely surprised by spending up to hundreds of dollars more than they thought they would by the time they get home from the airport.

Respondents' suggestions for improving air travel? Modernizing airport infrastructure, prioritizing the needs of passengers, boosting service and increasing options for travelers, regulating how airlines treat passengers, and increasing competition among airlines.