Some good advice above. What is your price limit for this lens? The lens is more important than the camera body as the lens is what gives you the quality.
Here's several options;
1) Nikon 55-200mm f4.5-5.6 AF-S DX Lens - £189
2) Nikon 55-200mm f4.0-5.6 AF-S
VR DX Lens - £239
3) Nikon 70-300mm f4.5-5.6 AF-S
VR Lens - £429
VR lens are more expensive but they produce better quality photographs and well worth the extra investment.
As mentioned above, alternately you could get a Sigma or Tamron lens such as;
4) 70-300mm f/4-5.6 DG OS - £399
5) 70-300mm f/4-5.6 APO DG Macro - £229 although this lens is a macro which meaning it's more suitable for macro shots than distance aircraft shots.
Above are just several examples of lens you could buy, personally, I would go with the 3 option, the 70-300mm VR lens for £429. Well worth the price and you could probably buy it for cheaper if you look around. Kingsavo's 55-200mm VR lens is also a good choice but might be a little bit limiting but should be good for Belfast City and Belfast international airports.
Hope this helps a little...
Dave
