“Advisory Routes” in Scottish FIR were Class F, IFR separated from IFR, but VFR permitted, I think without radio or transponder.
They replaced Airways beyond radar coverage.
EASA put an end to that, and they became E+, requiring either a Mode S or radio contact for VFR.
PS Is it true that Class F was the first airspace letter name, from the cockpit voice records submitted to the Airprox Board when airliners heading for Inverness EGPE encountered gliders from Aboyne and Feshiebridge gliding sites?
@Alpha_Floor – Wow!! Another thread from 2016 !!
Where have you been for the last 5 years? 
Regards, SD..
Alpha_Floor wrote:
I interpret it as temporary uncontrolled airspace that is in the process of becoming controlled.
That’s how it is intended to be used according to SERA (and ICAO Annex 11), but I’m not sure that’s alway the case. E.g. Germany used class F for airspace around uncontrolled airspace for a while before reverting back to G with RMZ.
I have flown there during my service days, in some death trap airframes & pannels, once low at night over empty land with other aircrafts, the sortie orders were always not to “bother civilian ATC, especially the Spanish”, I am not sure that SOP had to do with advisory airspace, region geopolitics, civvy vs mil friction, or just weak English RT scores in the squadron 
Class F is a weird one. I interpret it as temporary uncontrolled airspace that is in the process of becoming controlled. Kind of like road works in progress. Maybe a transitionary period from G to E where the authority needs to check everything works well, and in that period of time it is F?
At one time when I was very interested in the different classes of airspaces I was determined to find somewhere in Europe where there was a Class F. I couldn’t find any. One time, by chance, talking to a Canarias FIR ACC ATCO he mentioned something about Class F on some airways in the Canarias FIR. I couldn’t believe it because all Spanish airways are controlled, or so I thought.
I then found this in the AIP:
It points to a bunch of airways between FL145 and 195 thart overfly Western Sahara, a region with political tensions. For instance, UL660, running along the coast:
The airspace over Western Sahara above FL145 is owned by the Canarias FIR.
I then had a very interesting conversation with that ATCO regarding whether a pilot was required to comply with “advisories” while flying in Class F. I was of the opinion that a pilot does not have to comply, but he does have to communicate his intentions. He found this hard to believe at first but then finally agreed with me, although he told me that in practice the advisory service is provided as “de facto” control. And that neither he nor any of his colleagues actually give much thought to the fact that those airways are F FL145-195. There’s very little traffic flying in those levels anyway.
According to ICAO, advisory service is exclusively a class F thing. It’s what defines class F and what makes it different from G and E.
LeSving wrote:
Not according to SERA – and ICAO?
The phrasing of SERA does indeed suggest that advisory service can only be offered in class F — particularly the definition of “air traffic advisory service”.
bookworm wrote:
In class G, an advisory service may be available or it may not.
In class F, an advisory service must be available, but it does not have to be used by any flight.
In class E, an ATC service must be available, and all IFR flights must use it.
In classes A-D, an ATC service must be available, and all flights must use it.
Not according to SERA – and ICAO?
In class G, an advisory service may be available or it may not.
In class F, an advisory service must be available, but it does not have to be used by any flight.
In class E, an ATC service must be available, and all IFR flights must use it.
In classes A-D, an ATC service must be available, and all flights must use it.
I’m not defending….just describing!
