Jabawocky
Hmmm. interesting this one.
I first saw this myself more than 20 years ago in a high perf turboprob. Flying the same routes at the same levels it was VERY noticable that tailwinds would give an extra few knots on the IAS. Not just sometimes but always.
I have spoken to many perf bods about this and they all say the same: "not possible."
So there you have it. It doesn't exist except I have witnessed it plain as day as you now have too.
Someone, somewhere must have a simple explaination?????