While it was not initially made clear whether the photo had been taken before or after the plane had taken off, EasyJet has since claimed the seats were 'inoperative' for the flight.
A Twitter user called Matthew Harris uploaded the image, writing: "#easyjet beats @Ryanair to have backless seats. @IATA @EASA this is flight 2021 Luton to Geneva. How can this be allowed. GeneveAeroport @easyJet_press @easyJet."
The photo has already been retweeted 1,700 times since being posted earlier this morning, and also has 1,800 likes.
A reply from the EasyJet Twitter account asked Matthew to 'remove the photograph' so that the airline could look into it.
The tweet said: "Hi Matthew, thanks for bringing this to our attention, before we can investigate this could I ask you to remove the photograph & then DM us more info regarding this, so we can best assist you."
Harris then replied to EasyJet with what he claims is a 'real photo' of the flight descending to Geneva, adding: "Absolutely not."
Since the tweet started going viral, many Twitter users have commented to express their shock, branding the situation 'unsafe'.
One even joked: "The passengers behind have clearly paid for extra leg room. Now scoot over so they can put their feet up."
Others, meanwhile, have hit back about the legitimacy of the image, with one writing: "There is no evidence to suggest that the passenger pictured was allocated that seat for the flight. She is not wearing a seatbelt and is perched on the edge of the seat indicating she was there temporarily waiting for something to pass by in the aisle."
A spokesperson for EasyJet told LADbible: "No passengers were permitted to sit in these seats as they were inoperative awaiting repair. Safety is our highest priority and easyJet operates its fleet of aircraft in strict compliance with all safety guidelines."
Another wrote: "I don't think this row was in use. The lady is just sitting on that chair at that time, not strapped in. I'd be very surprised if she was actually allocated that seat for the flight."
Matthew Harris later tweeted an update that claimed: "This was her seat. The lady was moved to a spare seat once the flight was fully boarded. Not sure what would have happened if the flight was full."
Featured Image Credit: Twitter/Matthew Harris