Delta Air Lines and United Airlines planes at Chicago O'Hare International Airport.

Delta Air Lines and United Airlines passengers have sued both carriers, alleging they were charged extra fees to select window seats, only to find out that there was no window in their row.

Proposed class actions were filed against United in the San Francisco federal court and against Delta in the Brooklyn, New York federal court, seeking millions of dollars in damages for more than 1 million passengers at each carrier.

The complaints say some Boeing 737, Boeing 757 and Airbus A321 planes contain seats that would typically contain windows, but lack them because of the placement of air conditioning ducts, electrical conduits or other components.

Many other aircraft types contain similar peculiarities. For infrequent travelers, it can be confusing to know exactly what to expect, which is why tools like aeroLOPA, a site that maps window placement and other quirks of various planes, can be helpful to avoid the windowless window seats.

“For the more novice viewer, the biggest hurdle is determining exactly which aircraft type is operating their flight,” Gregor Milne, owner and creator of aeroLOPA, previously told USA TODAY. It can take a little detective work, cross-referencing the seat map shown on the carrier’s site with the more detailed layouts available elsewhere, to figure out what’s really on offer.

Passengers said Delta and United do not flag these seats during the booking process, unlike rivals such as Alaska Airlines and American Airlines, even when charging tens or occasionally hundreds of dollars for them.

The lawsuits say people buy window seats for several reasons, including to address fear of flying or motion sickness, keep a child occupied, get extra light, or watch the world go by.

"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 United complaint said. The Delta complaint contained similar language.

Delta and United did not respond to requests for comment from Reuters.

Contributing: Jonathan Stempel, Reuters

Zach Wichter is a travel reporter and writes the Cruising Altitude column for USA TODAY. He is based in New York and you can reach him at zwichter@usatoday.com.

This article originally appeared on USA TODAY: Passengers sue Delta Air Lines, United Airlines over 'windowless' window seats

Reporting by Zach Wichter, USA TODAY / USA TODAY

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