What usually gets left out of the discussion is that airplanes need more than a screen.
This shows some of the memory that I use to fly. As you can see, more memory is used by other add-ons that, I for one, wouldn't want to do without.
All totaled, my computer is using about 4.5GB to a little over 5GB on each flight.

(The GAPanel listings are for the two 9 inch monitors that I use for instrument panels.)
I don't even want to think about the memory limits of 32bit systems & FSX.