This can apply to countries that have water in between, like the UK-France or US-Canada.
- If an aircraft crosses into neighbouring country, does it need to go to a border-controlled airport (with flight plan and access granted)?
An IFR-filed flight with permission from that country's civil authorities, but to a non-international airport.
- Are international airports the only border-controlled airports or do some countries have predetermined airports that pilots can fly to, so that border control authorities can process them at said airport?