The United States do not have the ability to degrade or deny a gps signal based on location unless that particular location has a physical GPS jammer. I don't see what the US would gain from disrupting civilian airtraffic navigation. Just stop with your "either is a likely cause here"-spiel.
> The United States do not have the ability to degrade or deny a gps signal based on location
This was a feature designed into GPS from the beginning. They just stop transmitting the C/A code from satellites visible to the battlespace and a device can't bootstrap or maintain a location fix. Approved devices entering the battlespace (say a ballistic missile fired from a ship over the horizon) can continue to maintain high precision location using the P code.
Block III sattelites have also started transmitting M code, which is a second generation of military only GPS that claims to be unjammable and unspoofable.
In a major departure from previous GPS designs, the M-code is intended to be broadcast from a high-gain directional antenna, in addition to a wide angle (full Earth) antenna. The directional antenna's signal, termed a spot beam, is intended to be aimed at a specific region (i.e., several hundred kilometers in diameter) and increase the local signal strength by 20 dB (10× voltage field strength, 100× power). A side effect of having two antennas is that, for receivers inside the spot beam, the GPS satellite will appear as two GPS signals occupying the same position.
That's an ability to improve service for users of M-code receivers, which AFAIK are only available to the military (and it's new technology, so I'd expect it to be unsupported even by most military receivers currently in use).
The M-code is transmitted in the same L1 and L2 frequencies already in use
Nothing says that they have to transmit M-codes from the spot beam antenna.
In fact, since the M-codes are hardly used, it's pretty certain they're using that antenna for something else. How very convenient that those antennae are designed to transmit on the same frequency as the "ordinary" antenna.
Today I took the time to have a closer look. Turns out, the directional antenna for M-code is only present on Block III GPS satellites, and only four of those are currently in service:
So this is definitely not the correct explanation.
Besides, even if there were enough Block III satellites in orbit to provide constant cover of the affected area, it would still make little sense to tie up their most advanced capabilities to jam their own legacy signal, when you could just turn off the legacy signal when transiting the target area and provide your own military with continued service using the directional antenna.
And of course, Russia has its own satellite navigation system
> The M-code is transmitted in the same L1 and L2 frequencies already in use
Let's quote the whole thing, shall we?
The M-code is transmitted in the same L1 and L2 frequencies already in use by the previous military code, the P(Y) code. The new signal is shaped to place most of its energy at the edges (away from the existing P(Y) and C/A carriers).
