I agree! There was an air traffic control failure in the UK a few weeks ago, and I watched in amazement as they showed the live flights in the air across Europe, with any flights to the UK unable to land, and flights due to leave, unable to take off. They did it all manually, which resulted in massive tailbacks and delays. But the thing that struck me was the sheer number of flights happening at that moment in time as they kept showing live flight data.

As you say, it's not sustainable!