To my knowledge, AI fleets are not limited like player fleets, allowing them to have rather insane fleet compositions.
This is all good and well, for now, considering the player has the ability to make their fleet much more competent than the AI fleets, through more OP and/or aptitude bonuses.
Consider how your fleet is composed. Look into the logistics rating of each ship and see how they add up, as this makes a huge difference. I have two Conquests, six hammerheads, six shades, six afflictors, two tempests, and a tarsus in my fleet, and that pretty much caps me out. There are no actual cruisers, as I felt they weren't as functional as two destroyers, and often two destroyers weren't as functional as two frigates. Large fleets are difficult, particularly if you want to maintain maximum CR...
It'll be easier when the straight 25 ship limit is added, rather than logistics; though, I find the logistics part interesting, as it makes you have to think about fleet effectiveness rather than just dumping 25 cruisers onto the enemy.
