Major U.S. airlines said Monday that the booming U.S. economy is what led to a record-breaking level of travel over the summer.

"With a growing economy, steady employment gains, and household net worth at an all-time high in the first quarter of 2018 ($100.8 billion), passengers are taking advantage of persistently low airfares," a spokesperson for Airlines 4 America, which represents the largest U.S. airlines, wrote in an email to the Washington Examiner.

From the Wednesday prior to Memorial Day and the Tuesday after Labor Day, the Transportation Security Administration processed 253 million passengers and crew, a 6 percent jump from last summer.

The TSA said that nine of the top 10 busiest weeks in its 15-year history occurred this summer.

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Airlines 4 America said passengers are flying because of competitive pricing among airlines, an increase in the number of destinations, and because the industry provides the safest means of transport.

"Real airfares, including ancillary services, remain 20 percent below 2000 levels adjusted for inflation," the group said in its statement.

The Bureau of Transportation Statistics reported the costs of airline tickets are not rising at the same speed as the rest of the economy, which is good for consumers. In 2017, the average domestic airfare of $384 was at the lowest annual inflation-adjusted fare in 23 years.

TSA said, since Jan. 1, it has added 1,600 more officers to its ranks to deal with the uptick.