United Airlines says it plans to halt service at Kennedy International Airport in New York next month unless federal regulators let it operate more flights there.

Without the ability to expand its operations at the airport, United can’t effectively compete with other airlines at J.F.K., it said in a note to staff on Tuesday. United currently operates two daily round-trip flights to San Francisco and another two to Los Angeles.

“If we are not able to get additional allocations for multiple seasons, we will need to suspend service at J.F.K., effective at the end of October,” the airline said in the staff memo. “That would obviously be a tough and frustrating step to take and one that we have worked really hard to prevent.”

United’s chief executive, Scott Kirby, sent a letter last week to Billy Nolen, the acting administrator of the Federal Aviation Administration, formally requesting more space at the airport. In Tuesday’s memo, United noted that the airport had made infrastructure investments since 2008, including widening runways, but had not expanded flight capacity.

United resumed flying out of J.F.K. in early 2021 after a five-year hiatus, and for more than a year it has explored ways to expand there to better compete with other airlines. Earlier in the pandemic, United operated more flights at J.F.K. by taking advantage of capacity that wasn’t being used by other carriers, but now that travel has recovered meaningfully, those airlines have reclaimed their takeoff and landing authorizations.

In a statement, the F.A.A. said it was always exploring ways to safely and more efficiently use airspace in busy areas.

“The agency must consider airspace capacity and runway capacity to assess how changes would affect flights at nearby airports,” it said. “Any additional slots at J.F.K. would follow the F.A.A.’s well-established process of awarding them fairly and to increase competition.”

If United exited J.F.K., New Yorkers would still have access to the airline at La Guardia Airport and at Newark Liberty International Airport, which is a United hub. The airline is scheduled to operate more than 12,000 round-trip flights out of Newark this month and more than 1,000 flights out of La Guardia.