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.

Passengers sued United and Delta for charging extra for "window" seats without windows.

"Had plaintiffs and the class members known that the seats they were purchasing (were) windowless, they would not have selected them - much less have paid extra," the complaint against United said.