May I ask where you would fly and where from?
I have been at LGW flying for BA for a few years now, and I have had quiet a few autistic passengers over the years. We even have a child who is a regular traveller and who is autistic and most of the pursers know the family well now and we are very aware of the needs of this particular person.
Whatever your choice in the end I'd suggest you gave their cutomer service number a call, if anything else to reassure you!!! I am sure that many airlines can offer you a good service. SWith some airlines you can check in online, choose your seat online etc, so that might help take the stress away a bit maybe.
The situation you saw in december 2001 at LGW was a particular one as it was just after 9/11. I used to get shivers down my spine when having to pass near those policemen myself!!!
These days going through security might be the most stressful part of the whole experience, but that has nothing to do with any airline in particular.
I hope you have a very relaxed and pleasant flight!!! Enjoy the sunshine up there!!
