AUSTRALIA'S Qantas Airways has been forced to withdraw United States' advertising showing a man relaxing in an airline seat on a beach after it was revealed that the beach was in Hawaii. The slogan for both a print campaign and a 15-second television commercial was: ''You'll feel like you're in Australia as soon as you're on Qantas.'' ''It is obviously supposed to be an Australian beach but it doesn't identify the particular beach,'' Qantas media relations manager Ken Boys said. ''It was clearly an error of judgment. We've pulled the ad. They won't appear again.'' Mr Boys said Qantas' US advertising agency had shot the advertisement at Lanikai on the Hawaiian island of Oahu. ''The agency was doing a shoot in Hawaii for another client and suggested to our US marketing people that it would save a lot of money,'' said Mr Boys.