I happened to see in Beotrum that bombers in the SE corner of the map could not reach the capital immediately N of it.
Technically, the 2 capitals are connected by a line so the move should be possible...

... but after selecting the bombers, there's no way to make the airplane cursor appear when hovering on the selected capital because there's a bunker unit placed in the capital hex.
This means if i select the bombers and then select the capital, instead of allowing me to move the bombers it selects the bunker. The bunker can't be moved so it's a permanent problem.

Essentially rather than losing the bombers to this stupid issue, i preferred to surrender. It's a very troublesome issue indeed and i hope it's solved in a future patch.