Here's the new rule for booking the window seat: don’t assume it comes with a window.

Or else you’ll wind up as frustrated as these unfortunate passengers.

The hashtag #wheresmywindow has been building in popularity on Twitter as ripped-off flyers take to social media to complain about the lack of windows next to their window seats.

The no-window window seat phenomenon is becoming more common on planes, as airlines cram in more and more rows of seats and push out of whack the perfect alignment of seats and windows.

And these passengers are not impressed.

“Seat 9A...Window Seat...#wheresmywindow? I’m pretty claustrophobic and this really didn’t help,” Twitter user Schipffy tweeted at Qantas.

Another passenger, who recently flew with Turkish Airlines, tweeted a picture of the wall next to his seat with the comment: “This is my window seat, but there appears to be something missing.”

The awesome, sky-high views are really the only perk to sitting in the window seat — so what gives?

The team behind YouTube channel Today I Found Out tackled the issue in October, explaining it was due to airlines adding more rows of seats to aircraft to raise more revenue and keep airfares competitive.

While aircraft manufacturers decide where the windows go, it’s up to the airlines to decide where the seats go — and neither decision is necessarily made with the other in mind.

And in case you were wondering, it’s not a matter of simply adding more windows, pilot Karl Young explained on Quora.

“All airliner windows are only close enough to each other to have sufficient material between the windows to handle the stresses [of flying],” he said.

So that’s how we end up with window seats that don’t line up with windows, and Twitter feeds filled with frustrated, view-deprived passengers.

This article originally appeared on News.com.au.