"You should look like you travel often. But don't be dripping in designer clothing."
Another added: "When we fly, we have a strict dress code to follow. No jeans or trainers".
It comes after a jet-setting author revealed how she always manages to bag an upgrade to first class.
Briton Tilly Bagshawe told Bloomberg she's yet to pay for an upper class seat with the airline she uses most, Virgin Atlantic.
Ahead of her flight, she'll call the reservations team and say: "Have revenue management released any first-class seats for miles upgrades yet?"
She explains: "When they say no, ask them to check or just be put through to revenue management so you can ask when they will release some, as well as how many seats are left."
Bagshawe says the trick is to "politely respond like this: 'You have 20 seats unsold? Why aren't you releasing them?'"
She says that by the end of the conversation, the person on the end of the phone has almost certainly released an upper class seat for her.
A spokesperson for Virgin Atlantic said the airline releases thousands its reward seats for its most loyal customers.
