Geoffers, here's one for a start. The A139 is certified for SPIFR, as are other similar helicopters. Pilots are trained, licensed and tested to operate single pilot IFR. But a private owner or operator can require two pilots up front when flying passengers (it is an insurance requirement for some). Then, in some cases, the only time a SPIFR pilot flies by himself is during his check rides, or during positioning flights.