According to website Who What Wear, if you're looking to get bumped up, you just need to dress smart casual.
"It definitely helps your chances. When we fly, we have a strict dress code to follow," says one flight attendant. "No jeans or trainers - so i always go for tight black trousers and a blazer or a dress. For men, chinos or trousers and a shirt are worn."
Fortunately, it doesn't have to be top of the range of the stuff either.
"For an upgrade, it's all about looking the part. smart but understated," adds the flight attendant. "You should look like you travel often. But don't be dripping in designer clothing.
“It helps; someone who is potentially due to get an upgrade can be knocked back if they aren’t dressed suitably.”