How do you place static aircraft in fs9 scenery?

If you have a true static model (ie, a "building" that looks like an aircraft), you can add it using rwy12 or any other scenery editor.

If you want to use an AI aircraft model, you can make it almost static by giving it a weekly flightplan. Use AI Flight Creator and Traffic Tools, and add an aircraft that flies one circuit on Sunday at midnight. You can also use AFCAD to edit the parking spaces at the airport, if you want a particular aircraft to always show up in a particular spot.