Presumably you're thinking of Friday night - Sunday night?

I suppose there's no reason the aircraft couldn't position over to GVA or ZRH to make use of the empty leg, assuming there was a need there.

LON-SIR-GVA-duty somewhere else for the weekend-GVA-SIR-LON.

But you're asking a lot of passengers to stick to such a rigid charter. What about those who want Thu-Sun or Fri-Mon? Such people would probably rather transfer to GVA, given the wealth of choice that exists there.

You could, of course, let them combine LCY-SIR/GVA-LHR - but would that kill the route?

I was in Gstaad last week. Skied until 1630 - pretty much last lift - and then hoofed it to the station for the 1701 train back to GVA for a 2100 flight. (Thank you to the owner of the hire shop in Chateau d'Oex who agreed to meet us on the platform two stops further down and have two sets of skis thrown at him!)

Can't offer any suggestions as to how many bums you'd need to guarantee. But I suspect the reason it's not been done is the lack of marke. GVA is not quite inconvenient enough.

I'm probably wrong though...