It's not a bad shot, however there is a lot of general clutter in the image which detracts from it somewhat - the traffic bollards, the blast fence in the background and the shrubs at the bottom are examples. As you can also see by the jagged edges at areas of hgh-contrast (like the paint scheme curve on the nose, the white borders around the registration, and the 'crunchy' edge of the tail) it is also somewhat oversharpened.
The cure is not easy - and, though it might be salvageable, it might also take an awful lot of work. It's annoyingly in that boundary zone between being fine and just lacking that last kick of quality. However, as you say, it was rather speculatively taken with a long lens fro a substantial distance...
There are many tutorials on photo editing available. I suggest running through workflows and seeing what works for you. I am currently combining two separate ones, although I have yet to test them by submitting one, you can see my results in a contemporary thread...
- By Fergul
- and Jid.
Best of luck!