Complex situation here… I read a nice report (in french) here#:
It says that in this aera between switzerland, italy and france, it is commonly accepted to fly over borders without flightplan, if you take off and land in the same country.
Les trois administrations de l’aviation civile, parfaitement conscientes de la situation, ferment les yeux, sachant que le plan de vol n’apporterait rien à la sécurité des vols dans les Alpes.
==>The three civil aviation administrations, fully aware of the situation, turn a blind eye, knowing that the flight plan would bring nothing to the safety of flights in the Alps
I expected similar situation (except no collision) some times ago in a valley (Vesubie, 20nm north of Nice) where I was flying at crest level, but center right of the valley, monitoring Nice-info freq and plugged on 130.0 (the mountain frequency), I was reporting my location frequently but an helicopter just flew 100ft under me. I was heading south, sun in front of me, and the helicopter was below right, so under the engine (in a PA28). In the mountains, the ATC had no radar echo of the helicopter (but was seeing my transponder).
I fly with a stratux + skydemon but nothing seen.
I report the situation to the ATC, but he answered me that he had no other contact and it was golf class area, so the rules is to see and to be seen. Which is right, but insufficient.
Actually the helicopter was in a mountain area, and although I had no mountain qualification (I wasn’t flying to land on an altiport), I was following the rules. The helicopter was a professional company (I recognised it), he wasn’t doing the same.
If we had collided, nobody could explain that…
A few on this forum who are not members of the Megève aero club may still have had the pleasure of meeting Philippe Michel, the injured D140 passenger who is in hospital and on bail in Italy.
For them and perhaps for others who, seeing his family’s predicament, think “there but for the grace of God go I”, here is a link where folks can leave a small donation and a message of goodwill.
FYI: Here’s a Change.org petition in support of the Megève flight instructor (text in French only, but translates well via Google Translate).
Airborne_Again wrote:
At least in Sweden, fighters will be launched to identify any unknown aircraft approaching the national border.
I doubt they will launch fighters to identify a PA18 without radio and without transponder arriving with or without flightplan flying in G-airspace. I have many times reported traffic to Sweden Control, for which I received no information since they could not see them, arriving from Denmark probably without a flightplan or anything.
Dimme wrote:
I doubt they will launch fighters to identify a PA18 without radio and without transponder arriving with or without flightplan flying in G-airspace. I have many times reported traffic to Sweden Control, for which I received no information since they could not see them, arriving from Denmark probably without a flightplan or anything.
ATC can’t see them as they don’t have primary radar, but the military does! The military also gets all flightplans for border-crossing flights. So a PA18 without flightplan approaching the Swedish border would definitely be noticed.
In fact, FFK (The Voluntary Air Corps) the other year participated in a “readiness test”. The aircraft would fly very low (below primary radar cover) over the sea and then climb to suddenly appear on primary radar — without a flight plan or active transponder. The JAS39 Gripens appeared as expected.
Fortunately! 
In seriousness: how does military ATC match all those primary radar traces to the stack of flightplans that they have?
Airborne_Again wrote:
The aircraft would fly very low (below primary radar cover) over the sea and then climb to suddenly appear on primary radar
How you distinguish that from a grass strip VFR traffic with no FPL who just pop-up?
Ibra wrote:
How you distinguish that from a grass strip VFR traffic with no FPL who just pop-up?
Grass strips are not typically found over international waters.
Seriously, the question was originally about aircraft approaching a national border without a flight plan.
No judgment yet; the prosecution is asking for 7 years in jail.
