Air Force One
Air Force One touches down on the tarmac of Andrews Air Force Base in Maryland on 25 March, 2016 Getty

Perhaps no other head of state in the world gets the kind of tight security that is arranged for the president of the United States, and more so when he is on the move. While most of us are familiar with Air Force One, it is a lesser known fact that a low-profile but extremely powerful fleet of aircraft guard the main plane.

The secret air force consisting of three aircraft shadow the "official" convoy of Air Force One (a customised Boeing 747) and military transport that fly with it whenever the American president leaves Washington DC according to a Politico report. Although not technically secret, the fleet is rarely mentioned and the US Air Force has never publicly acknowledged owning some of them.

The fleet

The aircraft in the fleet are unarmed Gulfstream IV VIP jets known as C-20Cs purchased way back in 1985. Although they lack some modern controls, they are maintained in top condition and have a custom defence structure installed to prevent them from being shot down.

Each aircraft is powered by two Rolls Royce Tay turbofan engines and can carry between 12 and 16 passengers. The jets, part of the US Air Force's 89th Airlift Wing, are said to be less susceptible to the electromagnetic pulse (EMP) of nuclear weapons.

How does it assist Air Force One?

The fleet always follows the Air Force One, typically landing at airbases or airports an hour or less from the president's location. This protocol is followed so that in case the Air Force One is attacked or damaged, the president can be taken to the backup planes. The C-20s, therefore, have the ability to land on practically any runway as they need just half the length required for a 747.

In times of crisis, like war, terrorist threat or natural calamity one of the three C-20Cs may be used to ferry the president to safety. In 2000, President Bill Clinton is said to have flown aboard one of these C-20 Gulfstream planes into Pakistan.

Aviation writer Robert Dorr had earlier claimed that C-20Cs also follow the US secretary of defence when he leaves the nation's capital. This is primarily because the secretary of defence and the president are the only two people who can authorise the use of nuclear weapons in case of a war.

Reports earlier this year claimed that the current Air Force One jet is overdue an upgrade and may be replaced with a B-21, which has retro-fitted military-grade defence features. While it is not known when that may happen, the secret fleet of C-20s is keeping Donald Trump safe for now.