Ian
A market standard airline hull and liability policy is valid worldwide, there will be an exclusion for operating into certain countries (not for overflying) but would include a condition that commercial airlanes are open and the use of them and payment of overflying charges does not breach UN sanctions.
Operations into restricted countries, Iraq for example, can be agreed with the insurance market and would be charged based on the aircraft type, the type of passengers to be carried, how long the aircraft was planned to be on the ground and if it is a one off ad-hoc or a more regular service etc.
The one other thing I would add is the in the event that an aircraft was required to divert into an excluded country, say due to a critical tech problem to the aircraft whilst overflying, then normal insurance cover still applies even though prior agreement has not been reached with insurers (at a cost to be agreed after the event).
Does that help?
Clipstone.....