A good friend of mine is a retired helicopter pilot who did a great deal of polar bear work throughout the Hudson Bay region, in the high arctic, and he did some grizzly bear work in the western arctic. His primary gun was an 870 with an 18" open choke barrel, open sights, and with a pistol grip and a steel stock that folded over the top of the barrel. This is the gun that led me to hate folding stock shotguns! He also had an old Rossi Coach Gun with exposed hammers and a 6 round butt cuff although that was his house gun and I never saw it in the helicopter. He had an ATC and never flew without either his Dan Wesson or his nickel plated M-29 .44 magnum. Between the two he preferred the Dan Wesson and I was eventually able to talk him out of the Smith. Due to the nature of his work, your pilot pal should easily qualify for an ATC provided his employer will sign off on it.
Today the answer might be best answered by a pump gun with a 14" barrel and a Knox collapsible stock. Although this in no way takes away from the blackgun look, it is probably the best answer. I would probably opt for a marine coat finish, particularly if cracker shells were going to be used in the gun.
A Bush Pilot style Marlin '95 is an enthusiast's rifle. There are a few problems with it that are not shared by it's pump shotgun counterpart. First, there is little if any full power .45/70 factory ammo available in Canada so the fellow who chooses it must be a handloader. Secondly, the gun once retrieved must be assembled before it can be put into action. This may or may-not be a serious complication, but that depends on the nature of the work done by the pilot and the circumstances under which the firearm will be used, but clearly it is not as convenient as a gun that is instantly ready to go. Along with the assembly disassembly issue comes the fact that ease of assembly is directly related to the cleanliness of the mating surfaces and threads. A gun that is allowed to collect dirt will not go tother and that might prove a little inconvenient. Thirdly, the only type of ammunition that can be used in the rifle is lethal ammo whereas cracker shells and rubber bullets can be loaded in the shotgun. Again, the importance of this is dependent on the nature of the work he is involved with. Finally, bear defense seldom requires a long reach, but should the guy with the gun be required to protect a number of people working over a large area, it can happen. Under such circumstances his prowess with the helicopter will probably be what saves the day, rather than his prowess with a rifle.