Summer travel on U.S. airlines is expected to reach an all-time high this year on the wings of a strong U.S. economy, Washington-based trade group Airlines for America said on Monday.

The group estimates that about 222 million passengers will fly on U.S. airlines from June through August, up 4.5 percent from the same time last year.

U.S. carriers are increasing the number of seats available for booking by 4.6 percent to accommodate the demand, the group said.

"The continued rise in U.S. consumer sentiment and employment is leading to more people traveling more often," the group's Chief Economist John Heimlich said in a statement.

The top three nonstop international destinations from the United States are Canada, Mexico and the United Kingdom, the group said.

Strong U.S. domestic demand is poised to benefit American Airlines Group Inc., United Continental Holdings Inc., Delta Air Lines Inc. and others, while the lower cost of fuel — airlines' largest variable expense — is adding hundreds of millions of dollars to their bottom lines.