WASHINGTON (Reuters) - The Federal Aviation Administration (FAA) said on Wednesday it is again extending cuts to minimum flight requirements at congested New York City-area airports through October 2025, citing air traffic controller staffing shortages.

The FAA said the number of controllers handling traffic in New York is insufficient for normal traffic levels and that without "increased flexibility," congestion, delays, and cancellations are likely at JFK, LaGuardia and Newark airports.

Under minimum flight requirements, airlines can lose their takeoff and landing slots at congested airports if they do not use them at least 80% of the time. The FAA's waiver allows airlines to fly fewer flights and still retain slots.

Airlines for America (A4A), the trade group representing American Airlines, Delta Air Lines, United Airlines and Southwest Airlines, in April asked the FAA to extend the cuts, citing the controller shortage.

The FAA said in March it would relocate control of the Newark, New Jersey, airspace area to Philadelphia to address staffing and congested New York City area traffic by June 30.

The agency will require 17 air traffic controllers to move from New York Terminal Radar Approach Control (TRACON), known as N90, to Philadelphia. New York TRACON is one of the busiest U.S. facilities in the country.

In a letter to lawmakers this week, the FAA said N90 staffing levels have remained significantly below the national average for many years and the agency has been forced to routinely assign controllers six-day work weeks and slow air traffic in the New York area.

The FAA said the transfer of airspace would relieve the stress on N90 and allow FAA to optimize capacity.

The FAA said despite offering $100,000 lump-sum awards and other incentives, it did not get enough volunteers for the transfer that will last up to two years.

The FAA projects N90 will not reach 70% of the targeted staffing level until the end of 2026 and notes the current 25% training success rate will not outpace attrition.

President Joe Biden wants funding to hire 2,000 new controllers and reports have warned of the safety impacts of shortages.

American Airlines Chief Operating Officer David Seymour praised the FAA for "moving proactively to improve the operational reliability of our airspace" and said the slot waiver has significantly reduced delays for customers.