Just resync'd the internet clock and will leave WSPR running on 6m overnight looking for very long distance, multi-hop Es (ever hopeful), GDX and near continentals by tropo or aircraft reflections. Just got to hope the software does not stop working on my Win 8.1 machine in the middle of the night!
There is some debate about tropo versus aircraft reflection on 6m. David G0LRD is of the view that most of my 6m WSPR GDX is tropo, whereas I feel it is because of aircraft reflection, but only when the Doppler is low enough. Sometimes you have to wait hours and hours for this.
I'd much prefer it if these relatively long (for me) GDX paths were pure tropo, but feel the evidence points to aircraft reflections. The debate and evidence gathering continues, HI.