Glad someone mentioned FlightGear. It is a pretty nice simulator, with pretty accurate flight models, although not too friendly to setup. Once you do though ...

Glad someone mentioned FlightGear. It is a pretty nice simulator, with pretty accurate flight models, although not too friendly to setup. Once you do though ... . I used to do IFR practice in FlightGear, first for my IFR rating, then for the ATP. Unpublished holding patterns, weird approaches (single engine partial panel NDB was an ordeal ...), I could do thirty a day, free. It really helped. I would script random weather, instrument failures and clearances (with festival, I believe it was called). Not the same as a real airplane but still a very helpful tool.