Every once in a while, I have a terrific spotting experience. This has been one of the best.
I knew I was headed to ATL on business, so I wrote a request to the security manager and ops manager at ATL and requested permission to spot in the public areas of the airport. I got a very quick response, indicating they would be more than willing to give me permission. Two days later, I had my letter.
Three days after that, I'm on top of the South Parking Garage, and had been for about 3 hours, when a nice Atlanta Policeman stopped by and said I couldn't photograph at the airport. Gave me the standard "...since 9-11" routine. I showed him my letter, he (presumably) checked its authenticity and check my ID, and said "have fun." I didn't see the man or anybody else for that matter, for the rest of the day.
I guess the lesson to learn is: preparation is the key. Get permission. Alert them you are going to be there. I can't thank the ATL authorities enough for being completely responsive and willing to let me be a thorn in their foot for a few hours.
If you're interested and headed to ATL, the contact info for Ops and Security is on the ATL airport site.