Transportation Security Administration Chief Peter Neffenger testifies on May 25 before the House Homeland Security Committee. (J. Scott Applewhite/AP)

Long lines at the nation’s airports may continue through the summer, the result of record travel, understaffed checkpoints and changes made to reduce the risk of terrorist attacks, the head of the Transportation Security Administration told Congress on Wednesday.

TSA Administrator Peter V. Neffenger said that even with additional staffing help on the way, Americans could expect scant relief from long waits to clear security checkpoints.

“Clearly, the summer travel season is going to be busy,” he told the House Homeland Security Committee. “In the short term, TSA, airlines, airports, Congress and travelers working together can improve the passenger experience.”

With 97 million more passengers expected to pass through TSA screening this year than did three years ago, adding several hundred new screeners, paying overtime and giving part-time TSA workers full-time jobs won’t be enough to make the long lines evaporate, Neffenger said.

Committee Chairman Michael McCaul (R-Tex.) opened Wednesday’s hearing by ticking off a list of recent TSA controversies: three-hour-long security lines, scores of passengers missing flights at various airports, passengers stranded overnight in Chicago, 3,000 pieces of checked luggage that missed flights because of a breakdown in Phoenix, and an 80 percent increase in wait times at New York’s John F. Kennedy International Airport.

Here are four reasons so many fliers are getting stuck in long airport security lines. (Claritza Jimenez,Dani Johnson/The Washington Post)

“The American people are fed up with this,” McCaul said. The TSA “has struggled to keep up with the high demand and has been unable to put the right people in the right place at the right time.”

Neffenger said the problem of high volume and understaffing was exacerbated by one of his decisions: He ended a practice that allowed randomly selected passengers to pass through a special line reserved for those whose preflight background checks identified them as low-risk.

“I knew that that would dramatically increase the number of people back in the standard lines,” Neffenger said, “and we weren’t staffed at the level we needed to be to man all the lines.”

His decision was driven, in part, by a scathing inspector general’s report last year that said undercover federal investigators were able to slip weapons and phony bombs through the system more than 95 percent of the time.

“One of the discoveries in our root-cause analysis in working with the [inspector general] was that that introduced unacceptable risk to the system,” Neffenger said, referring to the practice of allowing randomly selected passengers through expedited screening lines.

The long lines snaking out from TSA airport checkpoints have been widely documented in news reports and videos of frustrated passengers. Neffenger’s trip to a Capitol Hill hearing Wednesday was his second to explain the problem.

His answer has been that it is the confluence of several factors: near-record numbers of passengers who arrive to fly at choice early morning and evening hours, decisions that reduced TSA staffing by more than 5,800 before Neffenger took over in July, and the procedural changes he thought were necessary at checkpoints.

Neffenger said TSA is projecting that 740 million people will pass through its screening process this year, up from 643 million three years ago. TSA staffing levels had been reduced by 12 percent when he was appointed administrator last year, and the 45,000-member workforce was scheduled to lose 1,600 more members in fiscal 2016.

“It was immediately apparent to me that one of the challenges we were going to have was to have enough screening staff to manage the checkpoints effectively,” Neffenger told the committee.

Congress acquiesced to his request to retain the 1,600 workers slated for layoffs. He said an additional 768 workers would be ready for service by June 15.

Neffenger said he also has other plans to reduce long lines. One is to introduce more airport dog teams trained to sniff out bombs. Another is to find funding to move the 20 percent of TSA’s trained screeners from part-time to full-time work.

The TSA also plans to actively promote enrollment in its Pre-Check program, the centerpiece in a trusted-traveler program that includes the Customs and Border Protection’s Global Entry program and other elements.

About 9.5 million people have joined trusted-traveler programs, which require visits to enrollment centers, background checks and fingerprinting. Those screened travelers are then allowed to use special lines with less-stringent requirements than those faced by other passengers.

Neffenger says that achieving the target enrollment of 25 million will significantly reduce the checkpoint delays.

“We need to expand the enrollment program,” he said. “I don’t think we have enough enrollment centers. The second thing is we need to make those centers more available, to do more mobile enrollment, and to streamline the enrollment process.”

On May 12, Neffenger told another House committee that he received daily reports on airport wait times and was confident that they had been reduced in recent weeks. This week, TSA declined to make those reports public, saying it was working to create a system to make them publicly available.

The TSA website relies on passengers to enter the wait times they experience in individual lines at airports. A recent visit to Baltimore-Washington International Marshall Airport showed that some of those times were wildly inflated by frustrated passengers.