New York’s Metropolitan Transportation Authority, the largest US public transit system, faces deficits that may grow to $918 million in 2029 after federal funding runs out, according to the Citizens Budget Commission, a watchdog group.

The MTA, for its part, has said federal coronavirus aid and additional payroll tax revenue will help balance its operating budget through 2026. The agency, which has yet to unveil estimates beyond then, is expected to release its 2024 budget proposal Monday.

However, the CBC, a nonprofit focused on state and city finances, estimates shortfalls will emerge next year. They will be manageable, in the range of $100 million to $400 million through 2028, but will then swell to $918 million in 2029, according to a report Monday.

“The MTA should start now to bring its spending in line with its recurring revenues, lest it return to taxpayers and riders for a new infusion of extraordinary resources in just a few years,” the group said in the report.

While ridership has increased since the depths of the pandemic, system-wide usage may still only reach 80% of 2019 levels in 2026, the MTA projects. Fare evasion and rising labor costs that exceed farebox and toll increases strain the system’s operating budget, according the CBC.

“Taking steps now to start closing future gaps will ensure changes do not have negative impacts on services or the economy,” the CBC said.

The CBC recommends running subways with one worker, rather than with an operator and a conductor on each train. The MTA should also improve maintenance and operating levels to find additional savings above the $400 million the transit agency anticipates annually.

An MTA spokesman didn’t have an immediate comment on the $918 million deficit estimate.