In the bin64 folder inside of your root FS 2 folder you will see different runtime .dll's these dll's are what tells FS 2 which mode to run. There is only one main executable that runs FS 2. Adding the parameter does not work at this time because of Steam needing to be open to launch a different mode other than the standard 2D mode. 2D mode(standard default mode) can be launched from Steam or by the desktop shortcut.
You can run Aerofly FS 2 with a command line option. To run it in Oculus Rift mode do
steam.exe -applaunch 434030 -othervr
If you want to run Aerofly FS 2 for Steam VR when using the HTC Vive call
steam.exe -applaunch 434030 -openvr
As drhotwing1 already mentioned, this will still start the Steam client first.