Actually, the designation Air Force 1 is for any plane carrying the President of the United States (POTUS). The powder blue United States of America livery is on many plnaes these days.

There is one plane (whose tail number I do not remember) which is usually the jet the President flies in.

As an interesting note, when Nixon resigned, he boarded a helicopter on the South Lawn (Marine 1) which took him to the plane he would be taking to CA. When he boarded, he was still President (Air Force 1). While in the air, Ford became President and the call sign of the plane changed, as it was no longer carrying POTUS.