Can a general aviation aircraft be forced to land when crossing the airspace of a country? I don’t know how to fly yet but my friend has a Cessna, he says it’s awesome to have and fly one and he also said he will take me for a flight one day.
I have been researching and reading online and I have a question because I’m a bit scared.
So in order to take your plane for a flight, you have to file a flight plan and when you are flying you have to, using the radio, let them know that you are on your way. Let’s say I’m flying from Italy to Germany by going over Austria and I have filled the flight plan and all the necessary paperwork.
Can the Austrians ask me to land in their country for any reason, even if I’m only going over their country to go to Germany and they have notified of this before the flight?
Will they shoot me down if I don’t comply with them and land in Austria?
So in order to take your plane for a flight, you have to file a flight plan


Usually incorrect. Flight plans are only needed for international and for IFR flights. But there are some countries where a FPLN is required for every flight, but not Italy, Austria or Germany.


  when you are flying you have to, using the radio, let them know that you are on your way


Only if you've filed a Flight Plan. If you haven't, then there's no need to announce your flight.


  Can the Austrians ask me to land in their country for any reason


They can, it's their country. But unless you're a criminal or a terrorist, there's probably no reason for them to actually do this.


  Will they shoot me down if I don’t comply with them and land in Austria?


If they ask you to land (see above) and you don't, then they could shoot you down. It's their country and they're trying to protect it. But it hasn't happened yet.