A glitch on United Airline's website saw thousands of passengers book first class flights from London to New York for £50.
The mistake was first spotted by a travel blog, which pointed out that if users changed their host country to Denmark, it was possible to book a return flight from London Heathrow and Newark's Liberty International Airport for 491 Danish kroner (around $75 or £50).
Passengers even had to choose only between business class or first class, flights that usually cost between £3,500 and £4,500.
Some excited passengers even took to Twitter to say they had managed to book the deal. However, according to Business Insider, the airline will not honour the "several thousand" tickets sold during the glitch.
A spokesman for the airline told the Daily Telegraph: "United is voiding the bookings of several thousand individuals who were attempting to take advantage of an error a third-party software provider made when it applied an incorrect currency exchange rate, despite United having properly filed its fares.
"Most of these bookings were for travel originating in the United Kingdom, and the level of bookings made with Danish Kroner as the local currency was significantly higher than normal during the limited period that customers made these bookings."
Speaking to the MailOnline Travel, the airline added: "United has temporarily suspended sales from its Denmark website because a third-party software provider applied an incorrect exchange rate and was misquoting the airline's properly filed fares.
"This error in the application of the exchange rate primarily impacted individuals who live outside of Denmark and who were not travelling to or from Denmark but were attempting to book tickets using United's Denmark site."
Wil.i.am vents on Twitter after United Airlines 'gives away' ticket
United Airlines flight to London turns back to Newark after smoke in cabin
United Airlines flight returns to Heathrow after maintenance issue