An ex RAF guy told me this one, dont know if its true....
They'd taken one of their aircraft(a nimrod i believe) for display at a US airshow
Anyway, in a vacant static aircraft parking space, they set up some cones and some parking chocks roughly around the area an aircraft would be. One of the crew pretended to be leaning on the ''empty air''., whilst another member walked around ducking under the ''wings'' etc.
This got the attention of a lot of people who gathered, not to mention a gaggle of USAF aircrew. The RAF crew then proceeded to explain to the americans about the RAFs new StealthBomber..apparently they believed it was really there.