No AIR BASE is needed?
The TT your planes are scrambling from still needs an AB.
As long as the TT with an AB is adjacent to the SZ from where your enmey is assaulting, whether or not the assualt is on the TT with the AB, your planes can scramble.
Btw…wasn’t that already the case in the original rules?
Yes and no. Coastal territories can now scramble. But when the coastal change was made (Alpha +1) originally only the territory that was being amphibiously assaulted could scramble to that seazone. For example, if the US tried landing in Korea, the airbase on Japan could not respond but an airbase in Korea COULD.
However, now it has been changed back, so that Japan could scramble to the seazone in response to an amphib assault on Korea.
This is gives much more flexibility to airbases (now that they’re restricted to a max of 3 scrambled aircraft). For example Germany can now scramble from West Germany to protect amphib assaults hitting the territories of Denmark, Norway, and Germany.