Many air carrier aircraft now emit ADS-B which makes their position visible to PowerFLARM. Before PF I had three interesting encounters.
Sorry to disagree, but there are two types of PowerFLARM... Not all work with ADS-B
PowerFLARM Core comes in two variants, PURE and ADS-B. The ADS-B variant has all the functionality of PURE, but with an additional SSR (Transponder) and ADS-B receiver for 1090ES. In addition to FLARM equipped aircraft, you will also be able to see transponder equipped aircraft. Aircraft without 1090ES ADS-B Out capability will be shown with approximate range and altitude difference (Mode-C). Aircraft with ADS-B Out will be shown identical to FLARM aircraft.