Hi Gian, thanks for using the forums.
Starting with the A380, the spot is just above the tail as can be seen in this equalised view:
With the composition on the A330, it looks quite unbalanced cropping close to the tail on the right but to the wing on the left; it's leading to a lot of dead space which doesn't add anything to the photo, so cropping a bit tighter on the left balances things out slightly:
And lastly, the final A330 shot. The main reason it was rejected the last time it was uploaded was actually due to quite a clear mark above the tail where something had been cloned or healed out, underexposed was tagged on as a secondary reason as something which would help improve the overall shot slightly. It's more the mid tones that could do with a tweak rather than the entire shot. Another quick note, some of your images do suffer from excess noise so maybe it would be worth looking into some noise reduction software. I gave the version you posted here a pass of noise reduction and a slight increase in contrast in the mid tones, it ended up looking something like this:
If you need any pointers on adjusting the mid tones it may be worth having a scan through this tutorial, I mention using Curves at the end which is what I used here. Feel free to post either here or at the end of that tutorial if there's anything I can clarify further. http://focusonflight.net/forum/viewtopic.php?f=16&t=12