WASHINGTON — The head of the Transportation Security Administration is heading back to Capitol Hill Wednesday to try to explain what his agency is doing to deal with increasingly long airport security lines that have already snarled the fledgling summer travel season. TSA Administrator Peter Neffenger is also likely to be pressed by members of the House Homeland Security Committee to explain exactly what prompted the ouster of the agency’s top security official, Kelly Hoggan. Hoggan was removed Monday and replaced by a former federal security director in Los Angeles and New York, Darby LaJoye. Neffenger has also announced a new management team in charge of screening operations at Chicago O’Hare International Airport. Long lines have been plaguing airports since early spring, but the issue came to a head in recent weeks when thousands of passengers in Chicago missed flights because of lengthy checkpoint waits. Changes announced Monday by Neffenger aren’t likely to have much effect in the short run, as the TSA doesn’t have enough security screeners to quickly scrutinize growing crowds of travelers and their sometimes overstuffed carry-on luggage. Neffenger has said the problem was created by a combination of factors, including the fact that more people are flying this year and fewer than anticipated have applied for the government’s PreCheck program, which allows passengers to move through security faster after submitting to a background check. Neffenger also said the agency will launch an incident comment center that “will closely track daily screening operations, shifting officers, canine resources, the National Deployment Force and other resources to meet mission demands in advance of predicted passenger volume.” TSA plans to add 768 new screeners by mid-June. Homeland Security Secretary Jeh Johnson, who oversees TSA and has addressed the security line delays in recent weeks, told National Public Radio Tuesday that TSA officers are being moved to staff checkpoints at the busiest airports at the busiest times.