Are peer-to-peer communications feasible between aircraft? I have several questions regarding plane-to-plane communications (P2P), by which I mean air-to-ground communications where instead of a satellite, planes act as the intermediate nodes between a given plane and its controller on the ground. Or in other words, peer-to-peer communication.

Would P2P be a feasible model for communicating between ground and aircraft? For example, could ATC or other operational messages be routed to an aircraft using a P2P method? Is this already possible? Does communication with aircraft require a satellite or terrestrial endpoint, or could P2P work instead? How much data and power would be required for all the messages needed for a typical transatlantic flight?
Yes, this we could do this.

Actually, we already do it: If an airplane cannot be joined by ATC, ATC will ask planes in the neighbourhood to relay the message.

As for what you are actually asking, which is a P2P mesh network for data or ATC, without active pilots involvement, this could work but would be completely impractical:

Mesh networks are still an active research topic (i.e., not exactly production ready), and offer little to no advantage over a traditional communication (satellite, aircraft to ground) that nobody would bother implementing this.

Few of the downsides are:


What if there is no plane to relay the message ? You are back to P2G (Plane to Ground), so why not use P2G in the first place.
What if there is a broken/rogue airplane that blocks/modify/fake your messages ?