Southwest Airlines sued flight-search site Skiplagged in Texas over displaying the airline's fares.
The lawsuit escalated the airline's legal fight, following a lawsuit against Kiwi.com.
"Neither Skiplagged nor Kiwi is authorized to display Southwest fares," the airline said.
Southwest Airlines filed a lawsuit against Skiplagged, a flight search engine, in a second legal challenge against flight-search sites that display the airline's cheap flights.
The airline said both Skiplagged and Kiwi.com broke its website's terms by displaying ticket prices. It previously filed suit against Kiwi.com. Southwest said it only allows online travel agents to sell tickets for its flights with the airline's permission.
In its newest lawsuit, filed last week in US District Court, the airline said the two travel sites appeared to be working together. It said Skiplagged's flight data came from Kiwi.com.
"Neither Skiplagged nor Kiwi is authorized to display Southwest fares or sell Southwest flights," the airline's lawyers wrote in the complaint.
Southwest didn't respond to a request for comment. A lawyer for Skiplagged declined to comment.
"We cannot comment on the latest lawsuit itself, but what is appearing here is a sense of panic from Southwest," a Kiwi.com spokesperson said. "Trying to hold back freedom of choice brought about through tech innovation with aggressive legal action is a sad situation from an airline that was a disruptor themselves."
Southwest in early June had sent a cease-and-desist letter to Skiplagged. In the exchange of letters that followed, Skiplagged denied the claim, saying it didn't scrape Southwest's website for info. Skiplagged also said it had removed Southwest's heart logo from its website.
"Given these facts, I assume it is not necessary to go into detail on the many mistaken assumptions and assertions in your letter," Skiplagged CEO Aktarer Zaman wrote in an email to Southwest in late June. "I trust this resolves the matter."
In the following letters, which were included in Southwest's lawsuit, the companies were unable to negotiate a solution.
"It is beyond dispute that Southwest routing information is widely available through multiple public-facing sources, which undermines [Southwest's] Letter's suggestion that Skiplagged is republishing confidential information," wrote Skiplagged's lawyer, Irwin B. Schwartz, of BLA Schwartz, in the final letter.
Skiplagged earlier this month filed a pre-emptive lawsuit in New York, its home state, asking a judge to rule on whether it had broken Southwest's terms.
By filing its new lawsuit in Texas, Southwest moved to keep its legal fight against the flight-search engines in its home state. Southwest sued Kiwi.com in Texas earlier this year.
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