Sikorksy’s VH-92A replacement helicopters for the President’s Marine One fleet are on schedule and slightly below previous cost estimates by 2.4%, or about $123 million.

Cost reductions came from a small number of design changes, stable requirements and efficiencies from cost saving initiatives, according to a report from the Government Accountability Office.

The US Navy plans to acquire a fleet of 23 VH-92A helicopters to replace the Marine Corps’ existing fleet of VH-3D and VH-60N helicopters. Initial delivery of the helicopters is scheduled to begin in fiscal 2020 with production ending in fiscal 2023.

The total development and procurement costs for the Presidential Helicopter programme is estimated at $5.1 billion, according to the GAO.

Despite steady progress, the GAO did highlight potential issues with landing the new Marine One helicopter on the White House South Lawn.

“The lawn is a highly visible, size-constrained landing zone where damage to the White House grounds needs to be minimised,” said the GAO report. “Currently, however, the programme is not meeting a key system capability requirement to land the aircraft without adversely affecting the landing zone (including the White House Lawn).”

The GAO did not specify what problems the VH-92A had with landing on the White House grounds. However, the programme is expected to implement a solution about five months after the start of production, though there is a possibility of increased cost and schedule delays if Lockheed Martin-owned Sikorsky has to retrofit aircraft after production is complete, according to the GAO.