I have a asuggestion. Limit flight distance for new airlines rather than flying to different continents.
I tried to start an airline in Iceland today. It's completely impossible. The demand is already very low (which is understandable), but in the real world iceland is in fact a very important hub for flights between the US and Europe as it lies right in the middle. My plan was to make flights to New York and to European cities, but alas, flights to New York are impossible for a new airline. No wonder there are currently almost no flights to Iceland.
My suggestion would be to limit the distance rather than merely flying to a different continent. This reflects the real world situation better.