This map shows every country in the world and their requirements for Overflight Permits and Landing Permits. For overflying aircraft, the yellow countries will want you to have a permit, and the black ones don’t. That’s for routine flights at least, if you’re on a Special Airworthiness or missing an engine, then pretty much everyone will want one.
Click on a region and you’ll get that …
And then click on the individual country to figure out what kind of overfly clearance you need.
OPSGROUP Members can also, or instead, make use of these tools in the Member Dashboard
Permit Helper will give you the full information for each country.
Airport Spy will show you the summary of Permit Requirements, along with any airspace warnings active.
For these tools, login to your Member Dashboard.