Orbitz has joined the suit against Aktarer Zaman, who last year founded skiplagged.com, a site designed to ferret out bargain plane tickets through a strategy called "hidden city." It skirts higher prices by allowing a user to buy a ticket with a layover in the flyer's actual destination, and the user just skips the last leg of the trip.
It only works if flyers travel without checked baggage and buy one-way tickets.
"[Hidden city tickets] have been around for a while, it just hasn't been very accessible to consumers," Zaman told CNNMoney.
United Airlines and Orbitz claim "unfair competition" and are seeking $75,000 in lost revenue.
CNN Money reported that travel experts expect that even if the site is shut down, others like it will just pop up in its place.
Zaman did not respond to CNBC's request for comment.