I am not surprised they can (i.e. they know the MTOW) because they have your a/c type and they look up the perf model for it and check the filed EET value for plausibility.
The margins they use are secret (as are all the perf models they use) but they are broad – 1.5x either way IME.
I would be amazed if the unix coders who get paid €10 per line of code (€20 per line of working Java code 
) would have failed to include a validation check option on every single parameter including whether the toilet is externally serviceable.
The motivation for banning light aircraft from airspace which is practically devoid of traffic anyway is something else, but we are never likely to find out, because only those working inside the system will know it.
I had few CTOT issued with the “symbolique 5min” this winter, not sure what is behind these?
However, it’s normal to get hit by +50min, I was told sometimes it’s CV19 staffing or restrictions on light aircrafts per sector per hour (SIV frequencies like Seine who take care of Echo are usually notammed U/S and the rest of ATC don’t offer much FIS/ATC bellow FL150)
Obviously not difficult to get around just adds extra uncertainty…
Ibra wrote:
I had few CTOT issued with the “symbolique 5min” this winter, not sure what is behind these?
Probably just to put you within a more predictable 15 min window (-5/+10) rather than a 45 min window (-15/+30).
lionel wrote:
Probably just to put you within a more predictable 15 min window (-5/+10) rather than a 45 min window (-15/+30).
Isn’t the window for IFR ±15 minutes?
So not much fuss there then !
-5/+10min is what I was told for Eurocontrol flight plans, seems consistent with EC NM mannual
Ibra wrote:
-5/+10min is what I was told for Eurocontrol flight plans, seems consistent with EC NM mannual
Yes, if you have a slot, but isn’t ±15 minutes the tolerance without a slot?
You maybe right, -5/+10 is only when you have a CTOT, for sure you need to notify changes or delays (send DLA/CHG or CNL/ACK to communicate new EOBT to IFPS), anytime the EOBT changes by +/-15min, so I imagine that is the tolerance without slot?
-5/10 tick the box if one is unsure 
Airborne_Again wrote:
Isn’t the window for IFR ±15 minutes?
I don’t immediately find an authoritative reference for the -15/+30 that I was taught. At least one other person on the Internet agrees with me: https://www.pprune.org/private-flying/603638-departing-early-vfr-flight-plan.html#post10005940
Several other informal sources on the Internet seem to agree with your -15/+15, as well as AIC A 15/21 of Austria; it says “Departure Tolerance Window (-15/+15 minutes around ETOT)”
I was taught -30/+60 for VFR flights, and I confirm that (when I was doing my PPL), at least one ELLX ARO person definitely agreed with the +60; someone on the Internet says -30/+30 for the Netherlands (https://www.pprune.org/private-flying/603638-departing-early-vfr-flight-plan-2.html#post10007255), and the +30 is supported by the now current AIP Netherlands ENR 1.10 section 1.4:
In the event of a delay (see note) in departure of more than 15 minutes for IFR flights (30 minutes for VFR flights) for which a flight plan or a flight notification has been submitted, the flight plan or the flight notification shall be amended, or cancelled and resubmitted.
Additionally, the AIP Belgium/Luxembourg ENR 1.10 section 1.3.4.4 says +15 for controlled flights and +60 for uncontrolled flights.
I don’t think pprune opinions are worth much especially as it clearly is country dependent.
Also it depends on how much effort your ATC unit is willing to put in on your behalf; for example if your filed FP has “lapsed” it isn’t actually deleted, it has just been moved to some database from where the “next authority up the food chain” can retrieve it, amend it, and re-file it. I’ve had that happen in France (where ATC seem to have very good access to flight plans) where I filed an FP for a few hours earlier
I am informed by someone in the system that there is no known function to limit the traffic to aircraft above a certain weight, e.g. 2t. You can limit particular traffic flows per sector though, including traffic at or below certain flight levels, and this will often hit the average GA traffic.
