The US Department of Defense demonstrated a rare aerial refueling of a Boeing E-4B aircraft, a flying command post known as a “doomsday” aircraft.

“In-flight refueling of the E-4B never becomes obsolete. God, what a knack it takes for this! The crews made a great flight,” Pentagon Press Secretary John Kirby wrote on Twitter.

He thanked the pilots and published a short video showing how refueling takes place.

The doomsday planes are designed to evacuate the country’s top leadership and control troops in the event of the destruction of ground and satellite infrastructure. The aircraft has the ability to refuel in the air and are accompanied by fighters in flight.