People standing up early on a landed planeI was pretty surprised to learn that flight attendants aren’t just being friendly when they greet you onto a plane – they’re also checking your sobriety, ability to help in an emergency and any additional needs. Some airline staff reportedly have secret codes for when they fancy a passenger too.But what about the etiquette we should follow as passengers? Plane rules might seem intuitive to those who spend hours on end in the sky, but according to Kim Deller, concierge executive at The Wedding Travel Company, many of us are missing the mark. Here are six of the rudest behaviours she sees from passengers all too often:1) Putting your feet on the seat Comfy as it might be, Deller considers this a cardinal sin.“The worst thing any passenger can do is put their feet on the seats,” she said.  “It’s unhygienic, unnecessary and impolite – and [it] shows a complete disregard for fellow passengers.”2) Taking