[CloCloZ]

When talking about TAS and IAS EVERYTHING is related to how many miles/kilometers you are travelling across the ground.
....

If you are saying that speed related to ground is related to both IAS and TAS, that's obvious ...
But if TAS is by definition "air distance flown over time" (as stated in one of your links), just TAS is significant about true speed related to ground.
Unless TAS just means "speed related to the air", in which case wind would be important.

Thanks for the info (I already knew the TAS/IAS relation with air density/temperature but is always useful to have clear references), although you didn't asked to any of my questions (but you haven't to do it, if you have no answers to some of them! :wink: ).

Anyway, I could guess that IL-2 computes TAS from speed relative to ground and that IAS is a derivated figure that, at SL on Crimea map, can differ from TAS by almost 20 km/h, that is much more than I expected on a map that likely shouldn't be "extreme" at least about temperature.

My question about what plane modders use as speed reference (TAS from IL-2 WW gauge, I suppose) remains.