IATA issues their Dangerous Goods Regulation usually in January and avalanche backpacks are described in Table 2.3.A „Provisions for Dangerous Goods Carried by Passengers or Crew (Subsection 2.3)”. It is a very good idea to print the table out, have it with you and in case of any problems with the airport staff questioning the avalanche backpack, kindly present them the regulation and insist that they also check it in their documents.
Also, you do not want to take the backpack as a carry-on – this usually causes problems, so just put it in the main luggage and enjoy the flight. Personally I have never had any issues transporting the backpacks, but in Japan our luggage was checked every time – it seems that the cylindrical cartridges always turn airport’s security heads.
The Japanese were very kind while checking the luggage and had clear manuals for that, but they hardly speak any English. So in case any problems arise, there will be hard to resolve them. Always remember that security guards are there doing their job so we all can fly safely – try to talk with them calmly and kindly, and I guarantee you will be good to go after some additional checking.
Some of the airlines offer ski or board quiver transportation for free, and it usually also needs to be reported. So to sum things up – a couple of emails or phone calls before the trip will quite surely spare you some problems at the airports. After all you are going for a great ski vacation and want to relax, right?