The amount of air travel this summer is setting records, but U.S. airlines are apparently not seeing related profits, citing increases labor costs and other related issues.

Such revelations are ahead of quarterly reports from airlines due out this month, and perhaps a warning that profits might not meet projected expectations.

Airports are moving record-breaking numbers, with nearly 3 million people passing have moved through checkpoints Sunday, the end of the July Fourth weekend, the Transport Security Administration reported.

Burt some carriers report weaker-than-expected sales because they've increased the number of flights.

Among the other challenges facing airlines is having to adjust hiring coming from the huge slowdown in air travel during the pandemic to the surge in post-pandemic flight, according to NBC News.

In addition, some airlines are facing delays in the arrival of new, more fuel-efficient aircraft from Airbus and Boeing. Meanwhile, an engine recall by Pratt & Whitney engine has grounded dozens of jets, the news outlet also reports. 

Delta Air Lines will on Thursday be among the first to release quarterly earnings numbers. 

There is a “weaker domestic pricing environment than we had forecast,” American Airlines CEO Robert Isom said at a Bernstein industry conference in May.

Carriers losing money have started to make changes: Jet Blue cuts unprofitable flights this year and discounter airlines such as Frontier and Spirit will begin offering bundled fares.