OT: looking at the maps on FlightAware, Flightradar24, and similar sites and seeing the vast number of planes crisscrossing the US at any one time I wonder if it would be possible to do a peer to peer navigation system?

A plane at 30k feet should have line of sight to any other plane within about 200 miles, and even farther the higher up the other plane is. If the other plane is at 30k feet, it should be in line of sight at about 400 miles.

Have a way for planes to exchange information with other planes that are in of sight about where they are heading and how confident they are that they are on the right heading.

So let us say you've got a plane flying from Los Angeles to New York. You see what other planes you can see. That should include others that are going to New York but are ahead of yours. Find out from those who confident they are that they are on course, and use that to figure out a good course for you to follow and an estimate of how confident you are in that course.

You in turn provide your course information to other planes heading to New York that are behind you.

I think you could probably make a viable system with omnidirectional transmitters on planes for broadcasting course and confidence information, and directional receivers for receiving those broadcasts.

I've sometimes wondered if some whales use a system like this. I remember reading once about some species of whale (I totally have forgotten which species and even where they lived) that had a long annual migration. Researchers had attached GPS trackers to several of the whales and recorded their routes.

The researchers were surprised by how direct the routes were. The various ways they had hypothesized that the whales might navigate would have enough uncertainty that they expect the routes to have a lot more deviation from the direct route.

The number of whales they attached trackers to was only a small fraction of the number of whales in the migration, and from what I read the migration doesn't start all at once. As the weather turns more and more whales start the migration.

Suppose the whales navigate like I suggested above for planes. The whales that leave early or using the imprecise methods that the researchers hypothesized. They go in the right general direction using clues like sun position, but can get quite a ways to the side of the straight route, such as when they lose sight of the sun.

The whales that leave a little latter would do the same thing. But the ones behind would also be able to hear the calls of the ones ahead. If they can tell what direction those are coming from, they can use that as a navigation input. If there are several ahead going toward the average position of the leaders should put the follows on a more direct route.

Even if there is only one ahead that you are following, as long as that one is on average going in the right direction you should end up on a more direct route. That's because if the leader is drifting side to side and you are going toward them which causes you to also drift side to side your drifts should have a smaller amplitude.

Those farther back following you will have even smaller drifts. The ones following your followers will be doing even better, and so on.

If the whales the researchers attached trackers to where all far enough back in the migration, the above mechanism might explain what the researchers saw.