You earn points for everything you shoot down, bomb and destroy. The more things you shoot down the more points you get. However, there are some limits. If you shoot down a plane and then die your points earned will be less than if you landed the kill.
You total points earn will be seen when you are in the hanger. Look at the bottom of the hanger window for them.
If you look at the plane or tank you were trying to use, you will also find it's one of the higher performance type vehicles. These planes are called perked planes. The Tiger tank is also perked. The reason is its heavy armor and long range main gun gives it an advantage on the field.
If you take another look at the perked planes take a look at the ENY value along with the points required to fly it. Also, look at the many different plans you can chose to fly. You will note some planes were flown early in the war and were not as advanced as models that were manufactured later. As a result the game programmers established an ENY value to each plane. The means if you chose an early model war plane and shoot down a hot rod, later model plane you will earn more points for the kill because you were able overcome the newer planes performance capabilities and still get a kill. Conversely, if you get up in a hot rod Jet, like an ME262 you are more likely to kill many of the older planes and will be not awarded as many points for the shoot down. Another limitation is if you die in that perked plane you lose the points and have to go back and shoot more planes down to earn what you lost.
There is one other concern that was set up to neutralize a one sided battle. If one country (AH2 has 3 in the Main Arena ) is has very few players the ENY value/cost to use hot rod planes will drop to allow an "equalization" of sides. And the country with 100 more players,. for instance, will hav a higher expense per plane.
BTW, since you are here reading the BBS. If you look above under DOWNLOADS, go to Help and download the help file. Information about the game, in an easy to read format, is at your fingertips in that file.
Hope this helps.