> No commercial aircraft is going to be allowed to take off with only 1/2 engines in operation.

That's a different question.

If you're knowingly flying into GPS jamming - these jamming operations are apparently announced via NOTAMs (https://news.ycombinator.com/item?id=28833002) - you should be planning ahead even more.

A pilot is responsible for having enough fuel in case of an emergency, like the GPS unit crapping out. Anyone running out of fuel due to GPS jamming was ill prepared for other emergencies.