WASHINGTON — The head of the Transportation Security Administration was heading back to Capitol Hill today 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.

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 many factors.