GPS is not essential to air navigation. It’s nice to have, and there are some approaches that legally require it to be operational in order to fly them (IFR procedures) but aviation has other systems in place to guide aircraft under conditions where visual flight navigation is impossible.

In this case, IMHO, the pilots had become complacent and lax in their navigational rigor because of the fact that GPS makes a lot of the slightly less automated systems unnecessary, and people get used to that workflow.

If the flight crew had been looking at their map and using it to inform them about the mountains in their path, fixing position by the VOR and DME, or even just a stopwatch and compass heading, they would have easily known they needed to be at a higher altitude. Not being precisely sure of their exact position, they should have at least been maintaining the minimum safe altitude for the area they knew they were in.

But unfortunately, people get so used to looking at the shiny screen giving them effortless situational awareness that they forget all of the rules and habits that kept pilots alive for the last century before glass cockpits were a thing, and they forget that mountains are the tigers of the air, always waiting to catch pilots unaware.

This is a useful cautionary tale not only for pilots, but increasingly for humans in general as we become accustomed to a new kind of instrument that allows us to offload a great deal of our cognitive focus to a tool that may sometimes fail.

> GPS is not essential to air navigation. It’s nice to have, and there are some approaches that legally require it to be operational in order to fly them (IFR procedures) but aviation has other systems in place to guide aircraft under conditions where visual flight navigation is impossible.

This has not been the practical reality for many years for IFR flights (arguably not for VFR flight either but some of the good old boys will still argue that you should still be using a map and compass).

In Europe the minimum requirement has been B-RNAV and aircraft are controlled with reference to intersections which have no defined relationships with underlying VORs, and an expectation of being able to navigate direct to one from any arbitrary point in space. Airliners generally get away with this because they have DME-DME disciplined INS. Smaller aircraft, well the backup is vectors from ATC.

Don't worry, our government is doing their level best to make GPS the only option for air navigation. After all, we all know that technology NEVER fails, and the sooner we can turn off all those big bad old ground radars and navigation aids, the sooner we can sell all that real estate and use the money for things that the American public desperately needs, like more corporate bailouts and bathroom security cameras.

Depends on the weather. A lot of approaches to airports are GPS only these days. If GPS doesn't work and you are not in VFR weather, you can't fly those approaches. In bad weather you'd be diverting to an airport that still has ILS.

Vectoring by the controller to a visual or ILS approach still works but they'd be juggling a lot of planes. And while lots of the bigger/older airports still have ILS, many VORs and DMEs are being retired and many smaller airports don't have ILS at all.

Denied access to GPS in a large area in bad weather would likely result in lots of flight cancellations and contingency plans getting put in motion to get anything still in the air landed safely. But controllers would get very busy and ILS runways very congested.

Here in Europe, there have been a few cases of GPS denied areas especially closer to Russia. Mostly pilots and controllers at e.g. Helsinki airport are able to deal with this.

This was the partial cause of Air France 447.

Pilots were so used to "the plane won't make a mistake" that they were not aware/not trained properly about things that are nothing to do with the FMS like frozen pitot tubes and also that the autopilot has a number of "modes" which mean you need to go back to basics like altitude, attitude and air speed.

I thought they were shutting down VORs to save money and relying more and more on RNAV (i.e. GPS) approaches.

To add to this, there's a good lecture called Children of the Magenta Line that discusses automation dependency: https://www.youtube.com/watch?v=5ESJH1NLMLs