the face of either of the pilot or the co pilot. they would focus on the instrument and on the manipulations of -- that are made. >> reporter: former ntsb chairman jim hall says cameras would be a deterrent to bad behavior or careless piloting and would be a key investigative tool. what could cameras detect? >> you can see the instruments, you can see what they're seeing on their instrument panels on their screens. you can see what they're doing with their hands. >> reporter: cameras on the instruments wouldn't necessarily give investigators much help in the germanwings crash probe. they already know how that plane went down technically. but former commercial pilot, lynn spencer, says cameras trained on pilots' faces could carved certain moments that cockpit voice and flight data recorders might miss. >> was the pilot choking, is the pilot having a seizure. >> reporter: the technology is already on the market but one manufacturer told us no airlines have bought their cameras. cameras are already used to monitor key missions like friday's launch to the