That’s already a rare event though, so the probability of it coinciding with a GPS outage is smaller still. Time integral of risk exposure and all that.

Rare as it is—and I’d argue it’s not as rare as some people think, having experience three avionics GPS loss-of-signal events in the past two years (in different aircraft)—they’d be nuts not to have considered that risk in the design. I can’t find the AFM supplement for Safe Return but to a first approximation, it wouldn’t be out of the question for it to go into a heading and altitude hold until it reaquires.

Surely they also use GLONASS and Galileo.