Delta Air Lines and United Airlines were sued on Tuesday by passengers who claimed they paid extra money to sit in “window” seats, only to find themselves placed in seats next to a blank wall.

Delta Air Lines and United Airlines have been sued by passengers who claim they were charged extra for a window seat but found themselves sitting next to a blank wall. The lawsuits, filed separately against the US carriers, seek millions of dollars in damages for more than a million customers of each airline.