Does ICAO approve world flight routes? If not, how are these agreed?

While ICAO doesn’t ‘approve’ world flight routes for international air traffic, it is instrumental to facilitating the cooperation and information needed to do so.

Indeed, ICAO’s seven Regional Offices emerged directly from the early Regional Air Navigation (RAN) meetings which world powers carried out post WWII, under the newly-drafted Convention on International Civil Aviation, in order to transition the many military air transport facilities and routes which had been established in the previous years to civilian use.

The required analysis and decisions for new or amended flight routes are undertaken by States through the Planning and Implementation Regional Groups (PIRGs) which ICAO has established in every world Region specifically for this purpose.