For air passengers who love to gaze out at wide blue yonder, few things are more frustrating than finding your carefully selected window seat and realising there's no window next to it.
It seems that in every few rows on a commercial jet, the windows don't quite line up with the seats, rendering the window pretty much useless.
So what's the deal with this annoying design oddity?
The team behind YouTube channel Today I Found Out has dug into the issue and shared the fairly rational explanation.
And it is this: 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.
Manufacturers such as Boeing and Airbus arrange where windows will be located in the cabin, with some thought as to where seats should go, and will pass on their seating recommendation to the airlines.
But airlines usually disregard those recommendations in favour of their own seating plans, usually so they can squeeze more and more rows of seats into the aircraft and decrease the seat pitch, or legroom, in order to raise more revenue and keep fares competitive.
Tracks on the floor of aircraft cabins allow rows of seats to be pushed closer together or further apart at the airline's discretion. It is also up to the airline to decide what seating configuration is used, such as a 3-4-3 arrangement, a 2-3-2, or the universally dreaded 3-5-3.
So the reason windows don't always match up with the seats is usually because the airline has crammed an extra couple of rows onto the plane, probably to make more money, and thrown the perfect alignment of seats and windows out of whack.