Ryanair, the budget airline, has been criticised by the Advertising Standards Authority (ASA) for using offensive language in an advert.
"Word play" has landed the budget airline in hot water
Published just before bonfire night, the advert depicted fireworks with the headline "Fawking great offers."
The ASA received 47 complaints from the public on the grounds that the wording was too suggestive.
The ASA upheld the complaints, while the airline responded by saying the advert was "intended to be humorous."
Ryanair added that the advert, which ran in The Daily Telegraph, was merely "word play" and did not believe it would cause widespread offence.
The ASA noted Ryanair's argument but concluded that the term "Fawking" was likely to be seen as play on a swear word and was therefore offensive.
The ASA has told Ryanair not to run similar adverts in future.
On Tuesday the European Commission ordered Ryanair to pay back some of the discounts it got from Belgian authorities to use Brussels Charleroi airport.
The Commission said the airline would have to repay a "reasonable" sum, which it implied would be about 4m euros.
In response, Ryanair vowed to fight the decision branding the Commission's decision a "disaster".