An American, an Australian and an Englishman are fixing the aircon on the roof of a skyscraper.
During their break the American says to the other two "have you seen how strong the updrafts are here?" "I bet I could jump off and it would blow me back up" with this he leaps off the roof and sure enough comes back up and lands on his feet. "Jesus, I've gotta try that" says the Pom and leaps off.
The Aussie turns to the American and says "you know you can be a real cvnt sometimes Superman.