WASHINGTON — The U.S. delivered the first two of a planned 159 U.S. UH-60 Black Hawk helicopters to Afghanistan on Monday, according to Capt. William Salvin, a spokesperson for Operation Resolute Support.

The helicopters were delivered to Kandahar airfield by U.S. Air Force C-17 loadmasters assigned to Charleston Air Force Base, South Carolina.

Two more UH-60s are slated to arrive later this week, Salvin told Military Times.

The UH-60s are part of a recapitalization effort to bolster Afghanistan’s fledgling air force. Gen. John Nicholson — the commander of U.S. forces in Afghanistan — told lawmakers  in February that strengthening Afghanistan’s offensive capabilities would break the stalemate in Afghanistan.

The UH-60s will replace Afghanistan’s aging Russian Mi-17 helicopters. Afghanistan’s Mi-17s have primarily served air lift and troop transport functions.

As U.S. and NATO air support to Afghanistan has dwindled over the last several years, the Afghan air force has been forced to take the reins while simultaneously beating back a resurgent Taliban threat.

Airlift capability has been a vital component to Afghanistan’s struggling forces. In 2012 U.S. aircraft airlifted nearly 265,000 tons of cargo, according to U.S. Air Forces Central Command air power summaries. That support has dropped to just over 57,000 tons in 2017 as Afghan forces have taken more responsibility for providing their own airlift.

UH-60s will be important for the Afghan air force in sustaining the airlift capability, however not all 159 UH-60s are slated to arrive this year, and the program is at the whims of a U.S. Congress approving funds every year to keep the program on track.

Only 53 of the planned 159 Black Hawks have been approved after Congress allocated nearly $814 million for the program this year, according to a report from Military Times.

Training to transition Mi-17 pilots to the new U.S. helicopters is slated to kick off in October, Salvin told Military Times.

Two classes will kick off simultaneously from October to November, according to Salvin. One class will be held at Fort Rucker, Alabama, with 25 pilots, and the other will be held at Kandahar airfield with 36 pilots, Salvin said.