Airforce one fuel tanks being cleaned:
Two pilots have to start all engines of Airforce one to empty the fuel tanks to clean them of dirty fuel.
As this is going to take some time the First officer states to have brought his pyjama's with him.
After some time, making jokes, both pilots check the fuel gauges and notice that very little fuel has been used... They wonder if an 747 can be so economical.. but there's no one to ask.. After a few more hours they notice the same result, when the captain took a look outside the window... where he saw this fuel truck parked under the left wing....
Informing the first officer.. he replied: "maybe the fueltruck needs to be cleaned as-well" as the captain asks him:"then what about the other four fueltrucks waiting in line"?