CTOT - ATC staffing

Sure; I said “most”.

Regardless of the actual reason, I think the strategy for the pilot is the same. If this is not correct, would you be able to propose a better one, @Guillaume? Your contributions are always valued.

They come about if the computer sees too much traffic going through a particular sector at a particular time. Essentially it models all the planned flights in the system and determines where they will be at a particular time. Obv things like strikes reduce capacity and can make it worse but eurocontrol slots are purely algorithmic.

I will check what happened on that particular flight. That won’t be before Tuesday. But from the look of the CTOT, I would say that the OP has likely filed the FPL less than 3 hours before EOBT.
Two things I can tell already :

• We are currently at the end of what we call the “week-end ski” season. It’s mostly brits going to ski resorts. This means that there is a high traffic demand to Alps airport (Lyon, Chambéry, Geneva, Zurich). Often the demand is higher than the offered ATC capacity. There is an agreed european plan how to handle that peak of traffic every week-end : https://www.public.nm.eurocontrol.int/PUBPORTAL/ in axis management section.
• It looks like Lyon is understaffed. As of january 2019, there is 76 ATC ’s whereas there should be 88 of them.

Now regarding ways to improve CTOT, in that case, I would have flown VFR in that airspace (I think the weather was fine yesterday), and you have to go visual at some point to reach LFHN anyway as there is no IAP.
Re-routing further west (ie flying through Clermont-Ferrand airspace) could work too, but you will need to head east at some point to reach LFHN.

Basically flying IFR in the Alps region during « week-end ski » is likely to trigger a CTOT.

As expected, the FPL was late filed (less than 3 hours from EOBT). That’s why the initial CTOT was bad.
The slot was due to a flow restriction within LFLL TMA.