No, over a million meteorological observations are collected each day by commercial airplanes, and these are a principle source of data for weather models. Weather balloons and other sounding instruments (satellites are capable of this) also make significant contributions, of course.

It's been proven for decades, the big problem with weather simulation is that the dynamics are chaotic. They continue to be, even as we collect more data from the surface and above. Our forecasts improve, slowly (by a day per decade or so, historically), but simulation cannot be accurate and precise in the same sense.

A good introduction is "Weather Prediction: What everyone needs to know"