US planes can land there. The territory to land on must be friendly at the beginning of the nation’s turn.
In the given scenario UK cannot land in the newly captured territory, as it has not been friendly at the beginning of UK’s turn.
On US turn the territory is British and thus friendly to the US.
Right about the carriers, but the Soviets did make extensive use of the Red Banner Northern Fleet cruisers and battleships in the defense of Leningrad; although these ships were essentially trapped in harbor at Kronstadt due to German mine laying operations, the guns provided a massive edge to the defending artillery - 12 inch Naval shells make an awful mess of panzer III’s 8-)
In 1944 the British battleship HMS Royal Sovereign and light cruiser USS Milwaukee were temporarily loaned to the USSR and served with the Northern Fleet