Which country has jurisdiction over incidents in flight?
In my PPL class I was taught a simplified explanation:

If a baby was born (or a crime committed for that matter) on an aircraft, the official country in which it was born depends on wether the aircraft's doors are open or closed (within reasonable limits, so assuming they can't be open in flight).

If the doors are open, the country will be the country where the aircraft is currently located. If the doors are closed, it will be the country in which the aircraft is registered.