There are wide swaths of the US airspace that do not have strong radar coverage, certainly not at 80,000 feet.
Most of the ocean is unmonitored, too. Remember MH370? We lost it in the air and we couldn't find it in the ocean. :-)
Most of the ocean is unmonitored, too. Remember MH370? We lost it in the air and we couldn't find it in the ocean. :-)
There was an article about that very topic on HN just recently. It was not even remotely over US airspace, and the pilot had evidently threaded the needle through the radar coverage of several nations.