If you are adding and testing for one plane at an airport where there initially were no planes at all, then note the following:

Note 1 ... After doing the compile, when testing to see if your plane appears ... run FSX and set the time to the scheduled (local) time the plane is supposed to appear. If it is not there, set the FSX clock BACK about half-an-hour. Check again. Still not there? Set the FSX clock BACK again, another half-an-hour. And maybe BACK again a third time if it is still not there. After doing that, reset the clock back to the scheduled (local) time for the plane but this time set the FSX clock FORWARD about half-an-hour. Check again. Still not there? Set the FSX clock FORWARD again, another half-an-hour. And maybe FORWARD again a third time if it is still not there. The idea is to check a good deal of time BEFORE and AFTER the scheduled (local) time.

 

Note 2 ... Due to a "randomness" factor built-in to the compile process, sometimes a plane that you have added (or edited) may NOT appear in FSX even after you have recompiled the traffic database and done checks as per Note 1 above. Just recompile a second time and test again, as per Note 1. And then if it still doesn't appear, compile again and test, a third time, to be sure. I've had cases where I compile and can see my plane ... but on the next compile that I do, the plane is gone and no longer shows. I just recompile again. This "randomness" appears to be there to help prevent congestion at airports and to also, well, create a random feel to everything. Who really knows? It can sometimes be a little annoying, but as long as you are aware of it, then you can work OK with it.

 

Both of these notes do still apply if you are working with (adding/editing) more than just one single plane.  But, obviously, when working with more than only a single plane, if things are working properly then you wouldn't be affected by, and shouldn't notice, the above points as much ... if even at all.