United Airlines and travel firm Orbitz have sued a website that helps users find cheap flights by picking out ones which stop over at the cities they are travelling to, according to court documents.
They argue that the site leads to "unfair competition" and have filed legal action in Illinois, United States, in an attempt to reclaim lost revenues of up to $75,000 (£48,000).
Skiplagged.com searches for flights such as one travelling from London to Sydney with a stopover in Singapore. Customers travelling to Singapore who take this kind of flight, rather than travelling directly, could save up to 40 per cent, the website says.
This only works for one-way flights and travellers cannot put luggage on to the flight when they check in.
The website's founder hit back saying he's merely using "inefficiencies" in the way firms price flights. He also said that by creating a website to help customers find them he isn't actually doing anything wrong.
Aktarer Zaman, the website's 22-year-old founder, told CNN:
[Hidden city ticketing has] been around for a while, it just hasn't been very accessible to consumers.