@henra
Dutch_M, you need to be awrae that you have to determine the kinetic energy always with regard to the relvant reference system.
For an aircraft that is the air surrounding it.
To make it easier to understand let's take an example:
You have a wind speed of 200kts. Your aircraft is travelling at 250kts.
Minimum speed of your AC is 150kts.
How much speed can you trade for altitude now?
Correct ! You can trade 100kts.
You will be flying backwards then with regard to mother earth, but aerodynamically who cares ? You will still be flying.
If the relevant reference system changes it's state beyond what the AC can bear, well then: bad luck. but you would have the same problem when you are flying at 100kts and suddenly a tailwind of 100kts hits you. Won't make a difference except for the horizontal component during impact with mother earth...
Hmmm, headwind, tailwind, airspeed, groundspeed ?
And yes, the speed bleed-off is limited by the aerodynamics to keep the airplane flying. Though speed bleed-off is not the same as loss in inertial Ekin.