There is an optional objective on mission 'Silgul' which tell you to build 20 Hades bomber.
I've build more than 20 bomber but it have not been marked.
I've got 6 airbase (3 in the screenshot) that made 4-5 bomber per each factory already and the objective still not marked.
Although there's a dialogue saying something like "you can go after his nexus now with that overkill fleet of bombers"
