Armchair sim-only pilot/aviation enthusiast, simply not having accurate wind speeds is enough to prevent a jet from landing because you don't have data to run p

Armchair sim-only pilot/aviation enthusiast, simply not having accurate wind speeds is enough to prevent a jet from landing because you don't have data to run performance calculations. Can you land without running performance? Sure. But now a standard landing is an emergency since you can't verify you have enough runway to come to a complete stop. (See SWA 1248 for what happens when you don't run landing performance calculations correctly in iffy conditions). This is, of course, ignoring all the other issues that simply not having accurate barometric pressure and cloud levels when flying IFR. If you're flying an approach that descends over mountains through a cloud layer and lack accurate weather data (specifically barometric pressure) then the chances of your EGPWS shouting "TERRAIN! TERRAIN! PULL UP!" because you're low due to an incorrect altimeter reading are non-zero. Do this in a mountain range and the EGPWS calls may end up being too little, too late even if you immediately perform terrain escape maneuvers given you still need accurate altimeter readings for EGPWS to function correctly. Accurate METAR reports are safety critical for aviation. Full stop.