Really some do, and some don't. But I think tons of Opensky aircraft have been converted so that they can fly in FSX. I think the 757, the 767, the A340, the CRJ-200, the 777, and the 747 have been converted to run in FSX. You can find them in the FSX civi jets section.
ALL of them work. Some (767, 747-200, 737) do not work immediately. Instead, you will have to go to another airplane like the default 747/737 and copy the panel out of them, then drop that panel into the downloaded planes folder.