Some folks are really lucky they live close to an airport where good shots are possible without much hassle. Other folks work at the airport and have some level of access. Some folks ask to be escorted (some credentials can help). Others have big zoom lenses.
Another lucky thing is to carry your camera with you everytime you fly. Get a good window seat and if it's daylight and the window is not too bad, you can get some interesting shots.
The example below was taken from the cabin thru a scratchy window. Needed a bit of PhotoShop processing to get close to acceptable...
Click for large version
Photo © Orlando Sotomayor