Video footage shows stains on a Ryanair flight as the airline was voted the dirtiest in the UK by passengers.
A poll of almost 8,000 passengers found that only 42 per cent rated Ryanair positively for cleanliness.
Nearly a quarter of passengers went as far as to rate cleanliness on the airline's flights as poor.
Overall, an average 81 per cent of respondents rated cleanliness positively across 42 airlines.
In the footage an undercover Which? investigator examines the cleanliness of a Ryanair flight.
She inspects her tray table and wipes the back of the seat in front of her with a sponge, remarking that "the dirt and grime are clear to see".
The wipe comes up visibly dirty and the researcher pops it into a plastic bag as evidence.
She then shines an ultraviolet light on the tray table that reveals stains not visible to the naked eye.
Other budget airlines fared better than Ryanair, with 68 per cent of easyJet passengers rating the airline's cleanliness as good or better.
Air New Zealand's cleanliness was scored good or better by 77 per cent of passengers, coming top of the list for UK operators.
