First, planes are upgradable, so you don't have that much planes at the same time.
You basically have 3 type of planes : fighter (intercept), bomber (bombard), and fighter bomber (can do both, but less efficiently).
Then, you have naval version, which are a bit less efficient, but can base on carrier.
The other planes are just flavour unit : a civ often has planes specific to it, and can build only that.
For instance, the Russian will build Su 27 interceptors, because they cannot make F 16 or Eurofighter : they won't build only the best one, but the one available to them.