NEWARK, New Jersey — Faced with congested airports, rising costs, a pilot shortage and a resurgence in travel demand, airlines are increasingly turning to the same remedy: bigger planes that fit more passengers.

Flights operated by the 11 largest U.S. airlines had an average of more than 153 seats on domestic flights last year, up from an average of nearly 141 seats in 2017, according to aviation data firm Cirium. In April, U.S. carriers have 0.6% more seats in their domestic schedules compared with the same month of 2019, despite operating 10.6% fewer flights.

The trend toward larger planes, part of a strategy known in the industry as “upgauging,” means airlines can sell more seats on each flight and make do with fewer planes, which are in short supply. While more passengers per plane drive down an airline’s unit costs, it means fewer flight options for consumers.

For example, United Airlines said its flights have 20 more seats per departure in its full network than in 2019.

Rodney Cox, United’s vice president of airport operations at the carrier’s hub at Newark Liberty International Airport, told CNBC last month that it’s difficult to increase the number of flights operated into and out of the airport, one of the nation’smost congested.

“The way we continue to grow our model and grow the business is to upgauge our flights,” he said.

Last month, United said it would fly about 3,600 domestic routes using wide-body aircraft. The airline also devoted 777s, the largest plane in its fleet with 364 seats, to fly between major hubs and Orlando, Florida, during spring break, a spokeswoman said.