Boeing has received a contract modification from the US Air Force (USAF) to deliver two commercial 747-8s for the new Air Force One aircraft.
The Federal Aviation Administration-certified aircraft, which will replace the two ageing VC-25A Boeing 747-200 presidential support aircraft, will be modified as per the requirements confirmed by the White House in March.
The aircraft modifications will include incorporating a mission communications system, electrical power upgrades, a medical facility, an executive interior, a self-defence system, and autonomous ground operations capabilities.
US Air Force acquisition principal deputy assistant secretary Darlene Costello said: "This award is a significant step toward ensuring an overall affordable programme.
"As we move forward, we will continue to seek and implement cost savings opportunities."
Presidential Airlift Recapitalization programme executive officer major general Duke Richardson added: "This award keeps us on track to modify and test the aircraft to become presidential mission-ready by 2024."
The USAF has also sought for proposals to design, modify, test and field two presidential mission-ready aircraft from Boeing.
The USAF awarded contracts for risk reduction activities for the programme last year, and is expected to start aircraft modifications in 2019.
Following a series of modifications and tests, the modified aircraft are likely to reach initial operational capability in 2024 to begin providing worldwide presidential airlift support.