SASless I think (out of my head, don˛t have the report at hand) NTSB after special hearing about HEMS safety in 2009 put together a list of reccomendations and one of them was to prohibit reverting to Part 91 after drop-off of patient (return-to-base flight) but staying under Part 135. Don`t know what FAA did with that reccomendation later.
In EASA land I believe this is not possible - HEMS mission is completed when you RTB - staying under AOC-Commercial rules until return to base. But, HEMS WX limits are quite low.
At first glance it seems these unfortunate guys really pushed the weather - but what is really interesting (and potentially lifesaving information) would be the background that brought this crew to such decision.
Last edited by hoistop; 21st Dec 2018 at 08:18.