This is not faked, it's not a hoax, it's not a fish-eye lens, and it's not distorted by the window. Nobody is lying, and most of the "I'm right you're wrong" analyses of this photo are complete shit.
But it is distorted. If this were the true curvature of the Earth, then it would indeed be a Small World After all!
Look folks, this isn't complicated. This was clearly taken out of an airplane window, by a small snappy-style digital camera. (I'd guess from about 15,000 feet from a small regional jet...Bombardier, me thinks...)
The apparent distortion is due to the camera's wide angle--the widest it can get, surely. It is not technically "fish-eye", because it's not so extreme as to produce a round image. Nor can consumer cameras get so wide as to produce objectionable distortion, or people wouldn't buy them. But there
is distortion. You can prove this yourself the next time you are faced with a vast apparently flat area--zoom all the way out, point the camera slightly down so the horizon line is high in the frame, and snap. The horizon will be warped. Just like this. Guaranteed. And yet, a photo of someone's face with the same zoom level will seem just fine.
The wing doesn't appear distorted because 1) it is mostly in line with the vertical midpoint of the lens, thus not warping vertically like the horizon. It
is however warping in the horizontal direction, it's just not very obvious. Furthermore, 2) The total amount of distortion is not that severe. The only time you notice it is in shots like this, with horizontal and/or vertical lines that drastically dominate the scene, and your brain knows they should be much straighter--the slightest deviation is overpowering. With the wing, your brain has not been hardwired since birth to know exactly what shape it should be, so you don't notice the distortion.
You can prove this to yourself: find you favorite little consumer-grade snappy digicam, zoom it all the way out, and take a picture looking perfectly perpendicular to a brick wall that consumes the whole frame. Then look at the picture. Any horizontal line above and below the midpoint of the lens will seem warped--more severely so the farther away from center, even though other photos--say, of your friends, or a wing--with the same lens setting will seem perfectly fine.
It's that simple. Pretty boring, huh. Hardly worth everyone getting all worked up over. Only on this forum could this happen.(Trust me, I've owned some 20 or 30 cameras of all grades and types, have been a semi-pro [not primary income] photographer for 20 years, have written countless advanced photo how-to blogs and articles, and have snapped several terabytes of photos since going digital in 2000.)