I received a number of inquiries about the FAA stop to all flights due to a system outage related to Notice to Air Mission. Here is the scoop about NOTAM and why it is a critical system.
A NOTAM (Notice to Air Missions), is essentially a message board system where pilots, air traffic controllers, and airport operators share safety-of-flight-related information. Pilots are required to check NOTAMs prior to flight. NOTAMs provide information such as runway closures, navigational aid outages, certain weather conditions like snow on the runway, obstructions, like construction cranes that suddenly appeared overnight, airspace closures due to military activity, aerial firefighting activities, and so on.
Checking NOTAMs is like checking the weather and traffic conditions before driving to work in the morning. The worst that is probably going to happen if you don’t check the weather and traffic is that you may be late to work or stuck on the side of the road. However, the consequences to an aircraft operation if the pilot doesn’t check (or can’t access) NOTAMs are far more severe.
Air traffic control (ATC) can provide any flight safety-related information to pilots that occur after departure, but there are too many NOTAMs for ATC to read over the radio frequencies all the time. In this case, aircraft already in flight when the system went down were not in any real danger, but it would be dangerous to take off without the NOTAM information.
For a more in depth look, here is an article from CNN on the topic:
I also did a quick video on the topic: