The nice thing is that receivers now pretty much have full redundancy with GPS + GLONASS. I assume that commercial aircraft use all possible signals including Galileo system.

I remember back in my engineering days when some of the first GPS receivers started to incorporate the GLONASS signal, controversial! I remember seeing my first demo of the GPS in the 80's with text-only display.

Looks like it was bad programming.

Altus Positioning Systems Pinpoints Cause for GLONASS Default : GPS World