All Delta maintenance work (in Atlanta) is performed at the TechOps facility, right on the airport at Hartsfield. The TechOps complex is located at the Northeast side of the midfield complex, along Aviation Blvd. Unfortunately, there isn't really any way to view the action at TechOps from land-side. You can view some of the ramp from Aviation Blvd, but much of the action is hidden behind the hangars.
If you're interested, the three primary maintenance buildings in Atlanta are (from East to West) TOC 3, 2, and 1. TOC 3 is the most recent hangar to be built, and houses Delta's in-house paint shops as well as three widebody maintenance bays. TOC 2 is the center hangar (the largest cantilevered building East of the Mississippi), and houses most of Delta's overnight, A, B and C checks for 777 and 767 aircraft as well as MRO
work for other airlines and the US Government. TOC 1 (the one with the "Fly Delta Jets" sign) is the oldest hangar in the complex and houses most of Delta's narrowbody work. Also in TOC 1 are Delta's back-shops, including the engine rebuild/MRO
operation and engine test cells. Let me know if you have any more questions - there's a LOT that goes on within TechOps, far too much to describe in one post.
If you're just interested in watching the aircraft taking off and landing, the only good place I can suggest is the main terminal parking garage at the West side of the field. Atlanta isn't very photographer-friendly, but the parking deck gives decent views and you shouldn't be hassled by security.
Hope this helps!
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