There are 3 plane classes in Metalstorm: Online. They are listed here and their uses are explained.
Aglity Class[]
These planes as the name suggests, tends to get agility bonuses, speed bonuses and evasion bonuses, and energy bonuses in their base stats. They are ideal in dogfighting as it allows you to turn towards your enemy faster. In versus mode and the campaigns this can help quite a bit. If only you are more agile than your enemy you will be able to hit once you two start turning to face each other.
Defense Class[]
These planes tend to have health bonuses or stealth bonuses. They Increase you survival chances by making you harder to hit and increase the number of hits it takes to destroy your plane. It is useually considered the ideal class for Survival Mode.
Weapons Class[]
A "Maximum Damage" class that receives bonuses that help it eliminate enemies as quickly as possible receiveing bonuses such as Missle Lock Range, and Damage. A great class to take out your enemies before they can reach you (counter to agility) If you can strike them down beofore they Reach you then you can survive much more easily. However If a Non-Weapons class plane is not destroyed before it becomes a turning dogfight you will be at a dissadvantage.