A record number of fliers is expected this summer, and the Transportation Security Administration is warning travelers: Get to the airport two hours early for domestic flights, or risk missing a flight.

Airports across the country are seeing lines balloon in size, thanks to a "perfect storm" of conditions  -- the number of airline passengers has increased to 700 million; there's massive attrition of TSA security screeners each week; TSA has cut staff by 10 percent over the last three years; and not enough passengers have enrolled in TSA's PreCheck program, the Associated Press reports.

Airlines have confirmed that wait times to get through security have surpassed an hour. Seattle-Tacoma International Airport says typical wait time is 90 minutes, Charlotte Douglas International Airport is reporting 75-minute lines, and Atlanta Airport tells the the AP that "things appear to be only getting worse."

The main culprit is that the TSA made a big bet on its PreCheck program and enrollment is moving slowly. TSA's PreCheck program, an expedited screening program, was supposed to be the answer to maddeningly long security lines at the airport because it's a quicker and lighter security check. But four years after its launch, only 9.3 million people had registered, a far cry from the 25 million TSA had expected.

"We had unacceptable line waits at the majority of our hubs," Robert Isom, chief operating officer of American Airlines, tells the AP. "Based on what the TSA is telling us, there is no relief in sight."

During the week of spring break in mid-March, 6,800 American Airlines passengers missed their flights because of long checkpoint lines, foreshadowing the headaches that airlines fear during the peak summer travel months.

If you need more proof of the soul-sucking long lines at the airport, search Twitter for #TSAproblems: