Long, long, long ago, when I was at Dobbs House catering, they trained us NEVER to park any closer to a DC-9 tailcone than the footprint of the horizontal stabilizer. Not only would this keep you away from the tailcone, but it would also prevent the horizontal stabilizer from hitting the top of the catering truck should the aircraft tip over on its tail during loading or unloading. I'm not aware of any DC-9 that ever actually did that, but keeping the truck that far back would have covered both possibilities.
We also had a policy at Dobbs that one couldn't "back-up" towards any aircraft. Seems someone at Dobbs in ATL did that to a Delta DC-9, hit the engine and thrust reverser, and did $55,000 worth of damage (this was back in the 1970s, so you can imagine that in today's dollars).
Wonder if AA made any policy changes after this one.
ALL views, opinions expressed are mine ONLY and are NOT representative of those shared by Southwest Airlines Co.