3 = 1

That is the equation that ought to be kept in mind when reading about China's finishing the construction of an old Soviet aircraft carrier and training pilots. For if China intends to operate her carrier at any significant distance from her home port in China, she will need at least three, if not four carriers in order to sustain one at sea.

Three is the bare minimum. Four is better. Four gives you one ship on station, one ship in a major maintenance availability (ie, an overhaul), one ship working up to deploy to relieve the ship on station, and one ship which has recently returned and is undergoing the training and maintenance to prepare for her next deployment. The four-to-one rule also applies to the escorts and the aircraft units.

A carrier that is conducting extensive air operations needs supply ships to resupply her on a frequent basis. The further away the carrier is operating from her base of supply, the more supply ships are needed. It could be that they will need five sets of replenishment ships to keep one carrier group at sea on an extended deployment, and that is with none of the supply ships out of service for maintenance and overhauls.

For a nation with one or two carriers, they are better viewed as mobile coastal airfields which probably won't be operating more than a few hundred miles, at best, from their ports. One or two Chinese carriers may unsettle the other nations of East Asia, but they will not be a significant threat to any other area.