WASHINGTON - Major U.S. airlines and aviation unions on Thursday urged the Biden administration to pause approvals of additional flights between China and the United States, citing ongoing "anti-competitive policies of the Chinese government."

In February, the U.S. Transportation Department said Chinese passenger airlines could boost weekly round-trip U.S. flights to 50 starting on March 31, up from the current 35, about a third of pre-pandemic levels. U.S. carriers were authorized as well to fly 50 flights per week but are currently not using all those flights.

Airlines for America, a trade group whose members include American Airlines, Delta Air Lines and United Airlines, and unions in a letter to the Transportation and State departments cited the "advantage Chinese airlines receive by continuing to access Russian airspace, while U.S. carriers stopped flying through Russian airspace at the start of Russia’s invasion of Ukraine in March 2022."

The letter, which was first reported by Reuters, was signed by the Air Line Pilots Association, Allied Pilots Association and Association of Flight Attendants. It called on Secretary of State Antony Blinken and Transportation Secretary Pete Buttigieg to "pause additional passenger flights between the United States and the People’s Republic of China until U.S. workers and businesses are guaranteed equality of access in the marketplace, free from the existing harmful anti-competitive policies of the Chinese government."

Flights between China and the United States - which were a point of contention during the COVID-19 pandemic - have emerged as a rare area of cooperation between the two super powers, but U.S. airlines have expressed concern about the rapid pace of increasing flights.

Airlines are worried the Biden administration could boost or even double to 100 the number of weekly flights permitted by Chinese carriers.

Separately, U.S. Representative Mike Gallagher, the chair of the House select committee on China, and the panel's top Democrat, Representative Raja Krishnamoorthi, urged the Biden administration in a separate letter Wednesday not to approve more flights until China abides "by its existing bilateral agreement, and passenger demand begins to recover."

The lawmakers said Chinese carriers "operate air routes at an anticompetitive commercial advantage that must not be allowed to increase without reciprocal parity in the number of U.S. carrier operated routes" to China. It added that "American passengers must not be exposed to unnecessary security risks by traversing Russian airspace."

More than 150 weekly round-trip passenger flights were allowed by each side before restrictions were imposed in early 2020 due to the COVID-19 pandemic, but until August 2023, Chinese and U.S. carriers could each fly only 12 a week between the two countries.

The number rose on Sept. 1 to 18 weekly round-trips and then to 24 per week starting Oct. 29. The USDOT approved 35 for Chinese carriers in November.

Reuters reported last June that newly approved Chinese flights to the United States were not overflying Russia, which would have given them a shorter flight time and fuel advantage over U.S. rivals blocked from Russian airspace.

(Reporting by David Shepardson in Washington; Editing by Chizu Nomiyama and Matthew Lewis)