Executive One is the call sign designated for any United States civil aircraft when the President of the United States is on board. Typically, the President flies in military aircraft that are under the command of the Presidential Airlift Group, part of Air Mobility Command's 89th Airlift Wing, based at Andrews Air Force Base in Prince George's County, Maryland. In 1973, to "set an example for the rest of the nation during the current energy crisis" and to "demonstrate his confidence in the airlines", then-President Richard Nixon became the only sitting president to travel on a regularly scheduled commercial airline flight when he flew on a United Airlines DC-10 from Washington Dulles International Airport to Los Angeles International Airport. A Nixon aide carried a suitcase-sized secure c