If you need a knife while performing Jumpmaster duties or jumping for that matter, it needs to be a hook knife. As OIC of both the Navy and SOCOM's Parachute Teams, the civilian market has already figured it out. Lightweight and razor sharp. If you are doing CRW, then you need two, one high and one low. For a Jumpmaster, I recommend a heavy duty EMS seatbelt cutter.
http://www.hookknife.com/hookknives.htm
http://www.square1.com/manufacturers/square1/p1155.asp