A permit is not required by the CAA for an overfly, but they do need to receive notification and will acknowledge the flight. You should do this one day before your flight. For private landings, you need to give notice via American Flight Support one day in advance.
Commercial landings require a bit more work. Firstly, you need to get a Transport Security Program which takes 60 days to set up. Then, you need to get a permit from the CAA for the flights.
For more details, contact our operation team at ops@americanflightsupport.com or call us at 1-888-245-4017