Surely:
If flying from your country to another country for approaches…
I just cannot see why 2 FPs are needed. I flew to the Alps from EGKA on just one FP.
While mobile data generally works, one cannot rely on it, and if you are hoping to trigger a DEP message that way, this is a definite no-no. Better to get somebody in the ground to watch you on FR24/FA and do it for you.
I have had to file 2 separate flight plans from Sweden to Denmark and back for IFR training (multiple approaches without landing) to an airport that does not have any beacon or IFR point to put in a STAY. The key difference however is that said danish airport has a tower, to whom I had talked to on the phone prior to departure, so they knew of and were prepared when I requested the closing/opening combo.
For circling Denmark’s main island Sjaelland during Covid shutdown (when landing was forbidden, but overflying was not), I used a single A-to-A VFR flight-plan.
In the US, ATC is not involved with VFR flight plans. Only FSS has a copy of a VFR flight plan. Activating a VFR flight plan starts the SAR alert clock. If you don’t activate the VFR flight plan, no one will come looking for you if you are overdue. FSS automatically deletes a VFR flight plan that has not been activated within 2 hours of ETD. For an activated VFR flight plan, an alert is generated by FSS if the flight plan is not closed at the ETA+30 minutes. Pilots are allowed to do round robin flights as long as the flight does not cross any national border and the flight plan can use airport identifiers as points in the route. With VFR, one does not need to fly their filed route nor are they bound to the filed altitude with the risk than if the aircraft goes down, the SAR effort will be more complex. Many pilots forego filing VFR and instead request VFR Flight Following from ATC and remain in radio contact. ATC will ask basic information and enter their own flight plan route since they don’t have access to what is filed. VFR flight following is an extra ATC service and may be denied if busy with IFR duties.
Cross border VFR flights require a flight plan to be filed. Crossing an ADIZ requires a DVFR flight plan including the point and ETA where the ADIZ is penetrated. Radio contact must be established where a transponder code is issued for the VFR flight through an ADIZ. The Mexico/US border is part of an ADIZ, the US/Canada border is not. Changes or deviations to the filed route require notification to US authorities.
Filed once in the air with SD on my mobile phone for a X border you still have a signal at 2000 Ft in most urban areas. Did it two hours before crossing. Called the ARO over Bluetooth to confirm the fpln had arrived. Flight plan opened with ATC while crossing the filed ADEP 1.5 hrs later. You need a co pilot while doing the adminstration in the air.
That happens anyway since in certain situations (reportedly all cross-border flights, with some other conditions) the departure airport does not receive your ARR message, so nobody finds out (readily) that you diverted contrary to C/I rules 
Plus, diversions are honoured without question.
German ATC requires several flight plans for IFR training missions without landing and that is done all the time
Why is that? The UK does not, for example. And within the UK no FP is needed anyway.
German ATC requires several flight plans for IFR training missions without landing and that is done all the time. The issue when opening a flight plan in the air or even after a touch and go is that you can disguise your real airport of departure. This can be used for circumventing customs and immigration as your final destination will only see your last flight plan in the system.
gallois wrote:
It would seem different countries have very different rules. In France an flight planned under IFR from Brest LFRB to Quimper LFRQ shooting the approach and going missed then returning to Brest would require 2 FPLs. You will receive your clearance for the return usually during the approach.
This is exactly the case for the situations I described above.
I have never done anything like this – not needed to.
The problem is that a lot of what should be possible is simply not implemented by ATC, whose procedures have not changed in decades. For example airborne filing is closely related to all this, is supposed to be available everywhere in the EU, but has never been implemented.
You cannot have two flight plans for the same time period but one can “hack it” so it doesn’t get detected. With Eurocontrol (I Y Z) one cannot do it at all but one can overlap two VFR (V) ones or one IFR (I Z Y) and one VFR (V) one because there is no checking across stuff which lives purely on the AFTN or purely in national databases – see the two links here. The Eurocontrol database is not cross checked against anything passing around the AFTN even though the latter all ends up in national (national security related) flight plan databases.
Of course a VFR flight plan is generally activated (DEP message) when you are airborne (an IFR one probably gets a DEP message done when you are off blocks (“EOBT”), so this topic is really about doing this after you have been flying around for a while, and now want to do a flight which needs a flight plan.
Another angle on all this is that “activating” is just a DEP message, and anybody with AFTN access can generate a DEP message for you. In the UK there is the AFPEX system available to private pilots.
Two identical topic threads merged.
Nope, that wouldn’t work either.
You should have filed the actual strip that you took off from as your ADEP. Just use ZZZZ in field 13 if it doesn’t have an ICAO code.
I had actually landed at a strip in Denmark and returned to Sweden the next day. But as I wanted to fly around a little bit I did not want to file a flight plan from the airport of departure and then having to stick to any track.
I therefore set up the plan at crossing airports with the plan to activate it when overflying. That is when the scolding began. What is curious is that ATC hinted that a touch and go would be sufficient to make them happy. I actually thought about doing a really low fly over the runway (the non towered airport was closed) and just tell them I did a TaG. 
Maybe the takeaway is that I should have used some kind of waypoint and not an airport.
