I surely have missed something: what is requried to invade a planet? I have done the following:
- build 3 fighters
- build 2 transport (with 2 transport module each)
- put the 5 ships in a fleet.
This fleet attack the planet and kills the defending ships.
After that, I am unable to invade the planet:
- the 5 ships fleet won't attack the planet
- after having split the 2 transports from the fleet, each transport or even the 2 merged in a fleet won't attack the planet

As i have a savegame, I will retry later in the day, but I would like to know if I have found a bug or if I have missed something before being able to invade a planet.