LOS ANGELES — A record 231.1 million passengers are expected to travel on U.S.-based airlines this summer, a 4 percent increase over last summer.

That was the forecast Wednesday from Airlines for America, the trade group for the nation’s air carriers. The prediction is good news for the airline industry, but it could mean major headaches for summer travelers who can expect even more gridlock at airport security checkpoint lines.

Based on booking demand, the travel site Orbitz predicts that Los Angeles International Airport will be the nation’s busiest for the Memorial Day weekend.

Wait times at airport screening checkpoints have been growing recently for several reasons, including a shortage of Transportation Security Administration officers and the growth in passenger traffic over the last few years.

“It has been a challenging spring with fliers waiting in lines that take more than 60 to 90 minutes to get through security,” said Sharon Pinkerton, vice president of legislative and regulatory affairs for the trade group. “We encourage TSA to quickly hire and train new staff.”

Congress authorized the Department of Homeland Security to transfer $34 million to pay for additional officers to reduce the delays. TSA officials said they plan to use that money to hire 768 new airport screeners.

But the union that represents TSA officer has called for the addition of 6,000 screeners. From June 1 to Aug. 31, the nation’s airports are expected to serve an average of 2.51 million passengers a day, a 95,000 passenger-a-day increase over last summer, according to Airlines for America.

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