Feral passengers are something any frequent flyer will have encountered on one or more occasions.
And Shawn Kathleen, from Columbus, Ohio, is no exception.
The former flight attendant was so fed up with her filthy fellow travellers that she decided to shame them on social media.
Appearing on Australian breakfast show Sunrise, the American former police officer and paramedic explained why she wanted to call out airline passengers with annoying habits - and the worst thing she's seen on board.
Ms Kathleen started her Instagram account Passenger Shaming 11 years ago - and the page now has more than 700,000 followers.
'I just felt like I needed to rant about the crazy stuff that was happening on board,' she explained.
'I feel like it's happening everywhere. We get a lot of photos of things happening in the terminal and obviously on the aircraft itself.
'I don't necessarily buy into "we don't have enough space" - it's an excuse to say that there's an issue that we can't behave like proper human beings.'
'I'm so sorry about the bare feet but yes, it's crazy,' she said, laughing.
She said she believed a growing number of travellers behaved badly on board because they have a 'sense of entitlement'.
'People think that they spend an X amount of money on a flight so that entitles them to treat the aircraft as they wish,' she said.
'Unfortunately, the aircraft is not your living room and you're on public transportation you're not on a private jet. So keep the personal grooming personal.'
While working as a flight attendant, Ms Kathleen said she saw countless feral airline passengers - but there was one encounter that stands out from the rest.
'The worst thing that I've personally seen was probably a gentleman who caught his hair on fire while he was in the lavatory during a flight smoking crack cocaine,' she revealed.
Passenger Shaming features pictures and video taken by disgruntled travellers and flight attendants from around the world.
The images include passengers getting a little too comfortable as they unashamedly spread their legs out as they nap, while others wedge their feet in between seats or near other travellers.
Filthy toes are caught on camera resting on armrests, while some women hang their long hair over the food tray of the passengers behind.
But the worst behaviour award certainly goes to flyers who think the perfect time to clip their finger or toe nails is when they're seated on a busy plane.
Other pictures show rubbish stuffed in seat pockets or strewn around the aisles.
Some people were caught in the act watching porn on their devices, with one man attempting to hide his screen, only to have the reflection appear on the window.
Other disgusted flyers were left shocked after they reached into their seat pockets to pull out a fellow traveller's dentures.
And during long-haul flights, some passengers decide to get change in front of others while many travellers find a new place to sleep such as the floor or against the wall with their feet up.
This article has been adapted from its original source.
© Associated Newspapers Ltd.