True. But what if there are more people competent to set up & maintain secure tunnels through the internet than there are people competent to set up & maintain dedicated fiber links?
But what if the actual bottleneck isn't the size of the various cohorts of people, but a bureaucracy that inflicts some irrational set of conditions that impedes competent operation? If so, then changing media won't help; whatever scheme you envision will fail.
I'm rather certain the FAA does indeed either employ or contract people that are capable of providing the solution. I'm also quite certain those people live in a perpetual blizzard of responsibility diffusion bullshit: the FAA is a venerable and highly risk-adverse operation. If someone told me it takes months of meetings and sign-offs to so much as log into a router and perform a benign check of some setting, I wouldn't blink.
Yes, but low-functioning bureaucracies are also the most prone to outsourcing. They can't manage to get anything done internally, so they hire outside orgs (hopefully higher functioning) to perform necessary basic services. Often late in the game, when (figuratively) a VIP visit could reveal that their bureaucracy is too broken to keep its office bathrooms clean.
In this case, that outsourcing could easily look like "call local ISP's, get connections, set up tunnel".
One of the more popular means of diffusing responsibility. A mere symptom, in other words. Not a cause. There is a abundance of qualified contractors in our world that could provide a functioning fail-over solution using whatever medium one might imagine. Somehow, this does not happen. The problem is elsewhere.
That seems like an extremely foolhardy thing to do.