I found these at the airstrip and got thinking about if you could make one work. I'm not a plane expert, but I did a little research and think you might be able to.

Takeoff conditions

The runway at the airstrip is in relatively good condition. Maybe pack some snow into a few potholes to be safe.

The snow is the biggest issue for the runway, but nothing a few days of back-breaking snow shoveling couldn’t solve. Just hope it doesn’t snow too hard for a bit.

The planes / Plane systems

There are two planes in the hanger with 2 more outside. The ones in the hanger are obviously the better choices as they were less exposed to the elements. There’s one with pontoons and one with wheels, but they can be swapped if needed. Not sure which would be better though the pontoons would reduce range.

All the planes share the same model with different paint jobs. From what I could tell, they are based on the Noorduyn Norseman aircraft and is what I’ll be basing the rest of this off of. These were produced between 1935 and 1959, so even in the MK.V, the latest one (and the one I looked into the most), as far as I can tell, other than the starter has no electronic components that are required to fly. The geomagnetic storm only affects electronics.

Some gauges do appear to be electrical by the fact they spin during aurora/fog, but other gauges don’t, meaning they are likely mechanical. You might want to go looking for a mechanical version in the parts area or, in the worst case, do some guesstimating about fuel levels and such. You’re gonna want to wait for aurora/fog to start it or improvise some other starting method.

Fuel

The Noorduyn Norseman uses aviation gasoline. There is likely still fuel lying around somewhere if not, siphoning from other planes is an option there is almost certainly fuel on the crashed aircraft in the lake not far off the runway if it didn’t spring a leak or lack of fuel was the reason for the crash. Worst case, you can use regular gasoline it's not good for the engine but might still work.

Another problem with fuel it might be frozen, as long as it's not contaminated most avgas freezes at −72 °F / −58 °C, which is possible in-game. The way you probably deal with this is getting the fuel container in a relatively small room with a fire and letting the ambient temperature thaw it out. This is likely the same with oils and other fluids.

Navigation / Landing / Destination

You’re gonna have to navigate exclusively visually, so look around for some maps and plot a course and wait for clear weather. Your compass won't work during the aurora, but idk about when it's not active, so use the sun, maps and, landmarks to figure out directions.

Great Bear is fictional, and its location has not been confirmed other than it's off the west coast of Canada and it's inspired by Vancouver but further north. On the globe model in-game, there is a large fictional island between Alaska and Russia, so some believe that is it, so I’m going off that as it is basically the worst-case scenario, but this advice still mostly stands if it's located more north or south. The range of the Noorduyn Norseman MK.V is roughly 1,125–1,450 km in favorable conditions you could increase this by flying light as possible and maybe jerry-rigging some extra fuel contraption.

So, assuming Great Bear is roughly at 64°43'46.21"N 169°27'00.18"W and assuming everything goes well, you can reach about either Anchorage or Fairbanks in 5 hours these are obviously major population centers and likely in chaos, so looking for smaller airports on maps may be better for fuel stops. Landing will likely be difficult with the snow. If you take the pontoons try landing off the coast or on non-frozen lakes, then possibly use an inflatable raft or something to ferry to and from land. Make sure you make a makeshift anchor for the plane.

After this, you should hop down the coast much the same. What you do from here is up to you and likely depends on the state of the wider world, but personally, I’d keep going to the tropics, loot some farming equipment, and live out my life self-sufficiently on some small island.

How do I fly a plane and do other plane-related stuff?

Your character in survival mode arrives via plane crash and is likely a pilot. If they were just a passenger, there should be some plane manuals lying around, so get learning.

Doesn't Mackenzie's crash prove this is wrong as he is flying the same plane?

No, he either had replaced some critical component like the fuel pump with an electrical version or something, or possibly the sparks and shock from the Aurora caused damage to other systems which likely would not have happened to these planes because they were powered down at the time (even if they are damaged, there are plenty of spare parts around). Plus, they were flying in a snowstorm.

This is just my uneducated ramblings if you know more about this stuff feel free to comment.