Last year when I was laid up with two broken legs, I needed soemthing that would work on my wife's laptop 'cuz I just wanted to do something with airplanes. I found an old copy of Flight Sim '98 or so that I had laying around. It ran perfectly on the laptop! Sure, the graphics created vacum pressure by oral means compared to FS9 and 10, but at least it let me fly something until I could get up and around. Flying with the keyboard took me back to the old "Aces of the Pacific" days, but it worked.
Although not FREE, you can find old copies of OLD flight sims and stuff at used game stores for nearly free prices. Might be an option.