Also, that sort of telemetry does exist for most major airlines, however it goes via satellite to the airline not the ATC.
Korean Air Flight 801 could have used someone 2nd guessing a pilot. They didn't until they were almost dead and then it was too late. Not 2nd guessing the pilot was a really really bad idea.
ATC doesn’t have the kind of situational awareness or manpower to fix these kinds of problems the vast majority of the time. It only seems like they could have done something after the fact when the disaster has already happened and hindsight activates.
Like the GP said, ATC second guessing pilots is a really, really bad idea. A few incidents doesn’t change that.
...yeah, the second pilot. And in this case, also flight engineer.
IIRC The problem was pretty much aside from errors the cultural issues with pilots, the "lower ranks" wouldn't dare to be assertive to seniority and just voiced the issues they saw without doing anything.
[1] In one case someone mixed imperial and metric unix, and instead of $something-kilograms, they put only $something-pounds of fuel.
Those who still do can be grounded and be moved into management or take up a career in politics.
It is a system built out of very regulated parts, very professional people, and tight controls.
Pilots are encouraged to be very forward and proactive about fuel situations because of https://en.wikipedia.org/wiki/Avianca_Flight_052
Minimum fuel requirements are calculated as "Time of fuel for cruise to certain points", which is usually good enough, but if an Airport is stupid busy, or has bad wind patterns, just a couple go-arounds will chew through your fuel way faster than the regulation expects.
Turbofan engines are also dramatically less efficient at low altitude than high altitude cruise. So holding at low altitudes because a congested airport is dealing with traffic will chew through your reserves much faster than you expect.
Ryanair flies short hops to congested airports. They will have relatively low reserves, and you should expect them to run into "Hey we are low on fuel" more often than international flights for example.
