Hi Dave
First off, congratulations on waiting for the plane, which absolutely makes the picture as you must have appreciated when you took it. Otherwise you would not have hung around for so long.
Personally, I prefer the original orientation. I did initially find the upward angle at which you shot took a bit of getting used to, which Is what I think prompted Peter's comment, but anything that causes a double take is no bad thing as people will usually want to take a longer look.
For me, it is the diagonals which dictate my preference. They are stronger compositional elements than horizontal or vertical lines and people invariably follow them from left to right, at least in westernised cultures and this seems to be consistent whether the viewer is right or left handed. (So far as I am aware there has been no scientific research into whether this also applies in societies which do not read from left to right. Most of the studies into human perception have occurred in the western world.) The most obvious diagonal is the gap where the sky is seen as it is the brightest part of the image and therefore attracts the eye first. The way you took it, this leads the eye to the plane, whereas the other orientation is directing attention out of the picture away from the plane. There are also the secondary diagonals of the building's columns which also direct attention towards the aircraft.
Then there is the plane itself. As shot, it is diverting the eye around to the left and this sets up a circular motion so that the eye is constantly circulating as it initially follows its natural inclination from left to right, before being lead back to the left and then back again. Flipped, the plane reinforces the inclination to follow a left to right route and out of the image. The plane is also in a better position in the original, as the bottom right hand area of the picture is the most dominant position, since this is where the eye ends up. The dark area in the bottom right hand corner holds it in and reinforces the circular motion. Being on the intersection of two of the thirds helps as well.
Sometimes flipping an image can improve it, but more often than not we instinctively select the composition which works best at the time of taking. I am sure that you could have shot the scene as shown in the second version and maybe you did. If so, what were your reasons for not selecting a different oriention either when waiting for the plane or when you came to choose the image to publish as your daily shot?