I just ran into the old runway reservation problem again, in a locally played savegame of the Bridgewater game. A single tile on my runway (north of Wallthorne Regis) was reserved by the wrong aircraft. I don't know why; I had lengthened the runway a while ago (same month). I've uploaded the relevant savegame:
https://ufile.io/6vdaydjc
Earlier, also in a saved BB server game, I've also seen a large bunch of planes by another player circling endlessly, but I don't remember where it was. IIRC I didn't even see an airport nearby, but I could be wrong about that. Probably the same problem.
This bug (or bugs) seems to have a long history - is there a known workaround, like having separate take-off and landing runways?
Sorry if the problem has to do with my airport design. I haven't played SimEx for years.
I have noticed the same problem on Stephenson-Siemens game. Usually opening the schedule of stuck planes helped to resolve the blockage.
At least in standard the unblocking tool for railways also works for planes. Maybe it is the same in experimental?