What are the benefits of using a aircraft carrier?

Answer 1

In the years between WW1 and WW2 military Aircraft became better in every measurable way, this culminated in them being able to carry thousands of tons of bombs or torpedoes.

Warships in WW2 had to deliver their weapons fire from a gun barrel or a torpedo launched off a ship which meant getting to within about 10-25 kilometers of the enemy depending on the type of ship and most front line ships moved 27-34 knots maximum speed. Aircraft moved 5-10 times that speed allowing them to launch from hundreds of kilometers away and return to their base in a relatively short time only risking 3-5 ton Aircraft and not a massive ship. They out ranged their opponents completely while striking within the same weight class compared to firepower.

Gaining air supremacy was especially difficult over the vast Pacific Ocean where real estate to build an airfield that was in range of an enemy was in short supply and in high demand for both the states and Japan so the Aircraft Carrier was essential. It provided an Ocean Airfield wherever one was needed. In the Atlantic they did the same thing but for the most part instead of aiming to sink an enemy fleet Carriers mostly British defended their Merchant Fleet from U-Boats. They also fought against the Italian Fleet in the Mediterranean.

Now days 10 are part of the US fleet and at 100k tons each they are 3 times larger than the Essex class of WW2 and launch advanced Fighter Jets not propeller fighters. They haven't fought any huge prominent Naval Battles since the clashes between the fleets of the US and Japan. They mostly bomb targets and provide fighter cover for invasions and interventions against nations whose entire yearly military spending probably costs less than just one of these new Supercarriers. There are other smaller Carriers in the World but now in 2013 all combined they weigh about half the weight of the 10 Ship US Carrier Fleet sans the 9 smaller VTOL Jet carrying Assault Ships.

The menial policing tasks of small wars keep them occupied until the next big war that hopefully never comes.