Summer travel on US airlines is expected to reach an all-time high this year, trade group Airlines for America said on Wednesday, adding to concern that travelers could face even longer airport security lines.

About 231 million passengers will fly on US airlines from June through August, up 4 per cent from the same period last year, the Washington-based group said in a news release. That estimate amounts to an extra 95,500 passengers per day, on average.

The group called on the US Transportation Security Administration (TSA) to quickly hire and train new staff to cut waiting times at airports. Security wait times have stretched longer than two hours at some US airports this spring.

US airlines have created a website for travelers to vent and share wait times for specific airports, and encouraged customers to enroll in a pre-screening program known as TSA PreCheck to help expedite security checks.

Separately, American Airlines Group Inc plans to spend $4 million on top of the $17 million it allocates annually to staff it contracts to help TSA officers stock bins at checkpoints and manage queues, Chief Operating Officer Robert Isom said in a letter to employees Wednesday, shared with Reuters.

TSA lines now "evoke frustration from all of us, as well as our customers who continue to miss flights due to lines that are literally out the door," Isom said.

Jeh Johnson, secretary of the US Department of Homeland Security, which oversees TSA, said on Friday that Congress had approved his request for $34 million to hire additional officers and pay overtime to manage the long lines. – Reuters