United Airlines on Friday became the third major U.S. airline to hike checked baggage fees for customers traveling in North America after American Airlines and JetBlue Airways announced similar increases.

United passengers flying economy in the U.S. after Feb. 24 will pay $40 for a first checked bag, or $35 paid in advance. A second checked bag will cost $50 at the airport and $45 in advance.

Maintenance and labor contract costs have risen for carriers while pricing power has weakened in the U.S. domestic market.

U.S. airlines collected nearly $6.8 billion in baggage fees in 2022 -- and $5.5 billion in the first nine months of 2023.

Four years ago, United raised prices for checked bags at airports by $5 to $35, or $30 if travelers pay in advance online.

This week, American Airlines raised fees for a first checked bag to $35 if booked in advance online, or $40 at the airport.

JetBlue said it was hiking checked baggage prices because "the cost of doing business has gone up significantly due to increased wages, higher fuel costs, and other inflationary pressure, and we remain unprofitable since COVID."

JetBlue said the cost of a first bag was rising to $35 if booked online in advance or $45 at the airport.

JetBlue said the price hike is "one step we are taking to return our company back to profitability and cover the increased costs of transporting bags."

Senator Richard Blumenthal, who chairs the Permanent Subcommittee on Investigations, said in November he was investigating airline fees for baggage, seat selection, and ticket changes.

In September 2022, the U.S. Transportation Department proposed requiring airlines to disclose fees for baggage, ticket changes and family seating the first time an airfare is displayed.

Congress in 2018, under heavy pressure from the airline industry, dropped plans to require "reasonable and proportional" baggage and change fees.

(Reporting by Kannaki Deka in Bengaluru and David Shepardson in Washington; Editing by Pooja Desai and David Gregorio)