Section 3.2 says “If the submitted flight plan is accepted by IFPS (on the continent), i.e. it is compliant with IFPS defined parameters, it will inform the airline that filed the flight plan that it has been accepted. This is sufficient for a flight to depart with local ATC approval. The flight plan will be sent from IFPS to all relevant ANSPs who need to manage the flight. For the UK this data is received at NATS”
I thought NATS had the ability to say to a plane at say Rome airport “I accept your flight plan but don't take off at the requested time but a bit later at xxx” In that way you can fly smoothly straight to your UK airport without say stacking, thus saving you fuel.” But this para is saying it has taken off before NATS gets to approve it. Is what I say a future plan that is not currently implemented (SESAR?)?
Secondly, note that due to national interests, it’s common for many ANSPs to have bespoke systems not found elsewhere. ANSPs don’t like to be told “Buy Joe Blogg’s off the shelf system” if only because they have some legacy systems they need to work around or like to favour their national suppliers. So NAS is bespoke to NATS (I think) for legacy reasons and so needs some special software in FPRSA to interface with it. Some here seem to be blaming NATS for needing a non-standard FPRSA but I suspect no others/few have a standard one either.