Expedia Group has filed a lawsuit against partner United Airlines growing out of a contract dispute.

The civil complaint, filed in Southern District of New York Monday, is under seal. The docket said the order would be filed under seal.

As of Monday afternoon, United's flights were still available on Expedia.com.

It is relatively rare that contract disputes between online travel agencies, on the one hand, and airlines or hotel, on the other, reach the public domain unless they are at a breaking point.

Airlines have gone missing on online travel agency websites in the past. One of the more high-profile disputes involved American Airlines and Orbitz Worldwide, which tangled over distribution costs and direct-connect issues starting in 2010. Orbitz took a substantial financial from the skirmish, which dragged on before being resolved in 2014.

An Expedia Group spokesperson decline to comment about its complaint against United. A spokesperson for United Airlines, citing pending litigation, wouldn't comment.

Although the cases are likely unrelated, Ryanair and Expedia are locked in a lawsuit in the State of Washington, with Ryanair alleging that Expedia accesses Ryanair's flight schedules and fairs without permission.