Ryanair, Europe's largest airline, attracted more than 1,600 complaints and is now under investigation by the UK's Advertising Standards Agency (ASA) after featuring a "jab & go" advertisement on their website.
The website featured an image of a syringe and a bottle that said "vaccine," along with slogans such as "book summer," "vaccines are coming," and "jab & go." Promotions for budget flights were also featured.
An ASA spokesperson said complainants claim that the advertisement "misleadingly suggests that the vaccine will have been successfully rolled out across the population by spring/summer and that travel restrictions won't apply by then" and that it is "offensive and irresponsible."
"In their view, it trivializes the effect of the pandemic on individuals and society," the spokesperson said.
The ASA said it will publish the findings of the formal investigation "in due course."