Aircraft carriers are next to go down after Tanks on the Battlefield.

The reason is because small AI powered handheld drones between the size of bees and the size of fish, can simply get through their defenses, and although the drones can't take out the carrier, they can blind the sensors down there, and after enough holes in the hull, the thing fills with water, and sinks. Of course you'll need a hundred thousand drones, all at once to do the job, but that's much less cost than the carrier itself.

The carriers are going to spawn porcupine cope-cages underneath with a button press.