An American Airlines plane. Getty ImagesAmerican Airlines filed a lawsuit against Skiplagged.com on Thursday.The filing comes one month after the carrier made headlines for punishing a teenager for trying to skiplag.Both United Airlines and Southwest Airlines have sued Skiplagged.com in the past.American Airlines has had enough of Skiplagged.com.The Texas-based carrier filed a lawsuit Thursday against the website, a fare-finding service that helps people book "skiplag tickets," or flights with the layover city intended as the destination.The suit, filed in a Texas federal court, accuses Skiplagged of deceiving travelers by selling American Airlines flights without a proper agency agreement, putting the tickets at immediate risk of invalidation.