It's an E-3 Sentry AWACS. It's not a spy plane, it's a radar control aircraft. That one looks like it's a NATO bird. I'll try to dig up other
pictures of it.
Here are some other examples. They're special paint jobs commemorating events. This one looks like the 50th anniversary of something.
that is the same as the ones i normally see here in the UK, the one in the op however was in the USA and seems to have a commercial paint job rather
than normal mil colours.