US advises its citizens not to travel to China due to the Coronavirus

This 'don't go there' is a 'level 4 'advisory.

The four advisory levels, from low to high regarding safety and security risk, are:

  • Level 1: Blue - Exercise Normal Precautions
  • Level 2: Yellow - Exercise Increased Caution
  • Level 3: Orange - Reconsider Travel
  • Level 4 : Red - Do Not Travel

With this, a blanket advisory for the whole of China, how far away can a stop to air traffic between the two countries be?