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A projected 14.2 million people will fly during the Labor Day period, a 3 percent increase over last year, according to Airlines for America.

Strong profitability has positioned airlines to handle the increase, as Delta and others have invested billions in service, technology and flight capacity, said A4A, a trade organization for leading U.S. carriers.

During the seven-day Labor Day travel period from Wednesday, Sept. 2, through Tuesday, Sept. 8, A4A expects 2 million air passengers per day, up 59,000 daily passengers from the same period in 2014.

Friday, Sept. 4, is expected to be the busiest day.

“A4A projected an all-time high for summer travel this year and year-over-year increases continue,” said John Heimlich, A4A Vice President and Chief Economist. “With capacity increasing and airfares trending downward, air travel continues to be more accessible and a bargain for cost-conscious consumers.”

Ten airlines – Delta, Alaska, Allegiant, American, Hawaiian, JetBlue, Southwest, Spirit, United and Virgin America – collectively reported a net profit of $8.7 billion, up from $3.9 billion during the same period last year. The improvement was driven largely by lower fuel costs.

Meanwhile, in the first half of 2015, the 10 airlines collectively reinvested $8.5 billion in their businesses, A4A said. New and refurbished aircraft are being delivered at a rate of nearly one per day. Additional investments include route expansion, development of mobile technology, and enhanced airport check-in areas, lounges and gates.

Delta recently unveiled a $229 million renovation at Los Angeles’ airport, and announced it will partner with state and local officials on a $4 billion redevelopment of New York’s LaGuardia. The airline also announced upgraded and increased flights from New York’s JFK to LA and San Francisco, for another example.

“Six years post-recession, airlines are finally realizing profit margins that are on par with the S&P 500 average, a barometer of U.S. corporate performance,” said Heimlich. “Improving finances have accelerated their investments in people, products and technology to enhance the travel experience for customers.”