I think maybe it is a mission which can't be changed. I'm not sure though, but I seem to remember having the same problem with some missions. Keep trying though...I hope someone can help.
You could also try looking for a single mission for the Bf 109 with a ground-start.
Also I think the second mission in the Redux campaign (Luftwaffe version) has a ground start. I just started it myself. The (Luftwaffe) Redux campaign is made by Heinkill, and has reworked and improved missions. Here it is:
http://forum.il2sturmovik.com/topic/...-campaign-cod/
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