A booming economy and high consumer confidence levels led to record-high air travel in the United States this spring, according to government and industry experts.

The Transportation Security Administration on Monday reported processing 72.1 million passengers during spring break, which runs from March 15 to April 15. That's nearly 5 percent higher than the same period last year.

[Related: Trump takes credit for safest year ever for air travel]

Airlines for America, which represents the largest U.S. airlines, expects an additional 6 million more people to board planes for travel from March 1 through April 31 compared to the 145 million who did so in the same period last year.

TSA spokeswoman Lisa Farbstein explained the increase in two simple words: "good economy."

AAA attributed the increase to a perfect storm of conditions.

"AAA travel agents report a strong interest in travel last year and into the beginning part of this year, thanks to a strong economy and growing consumer confidence," John B. Townsend II, public and government affairs manager for AAA's Mid-Atlantic division, wrote in an email. "Now a dark cloud is rising on the horizon, higher prices at the pump. Yet it seems that more expensive gas prices have not kept travelers home so far this year."

TSA processes an average of 2.1 million passengers per day, but screened up to 2.5 million people each day during spring break.

“Travelers are taking to the skies this spring in record numbers, thanks to persistently low fares, unsurpassed levels of investment in the product, increasing competition, and unprecedented access for passengers of all regions, age groups, and income levels,” Airlines for America Vice President and Chief Economist John Heimlich said in a statement last month. “An expanding economy, employment gains and surging household net worth are also contributing to the growth in demand for air travel.”

The busiest U.S. airports during spring break were LAX in Los Angeles, JFK in New York, and ORD in Chicago.

TSA Administrator David Pekoske noted 95 percent of all passengers waited less than 20 minutes at security checkpoints.

People who flew in 2017 cited personal reasons, not business, as the reason for travel, which reflects "both an improving economy and the increasing availability of affordable, accessible airfare options for the average American and their family," according to A4A.

It's not just the airline industry that has seen a bump in travelers. The U.S. Travel Association reported a 3.6 percent year-to-year growth in all U.S. travel, including trains, automobiles, and buses, as of October.