"Activating" one Viper can be one of three things: Launch one unmanned Viper from one of the red spots on the side of galactica, move one unmanned Viper to an adjacent space area or attack with one unmanned viper (that is shoot at ONE Cylon ship in the same area as the Viper). So the two activations from the command area, can for example, be used to launch a viper and move it to an adjacent space or attack with one Viper TWO times. Or any other combination of the three options, two times. As explained above, Lee Adama's once a game action ability lets him do the same,just six times instead of two.
Now, if you are piloting a Viper yourself it is a bit different, because you can use your characters "move" to move the Viper you are piloting (your little red disk is underneath), and then you can also use your action to "activate" the Viper. So if you begin your turn in a Viper you could use your move to go to an adjacent space area and then use you "action" to "activate" the Viper with another move or an attack. Also launching yourself with an action from the Hangar gives you another action, which could be used to activate the Viper. You can never "activate" a Viper being used by another player using the Command action area or Lee Adama's ability.
The main advantages to piloting a Viper yourself comes from the pilot skill cards, that can let you reroll an attack against you with -2 or let you attack 4 times. Starbuck's special ability also lets her take an extra action if she is piloting a Viper at the start of her turn. So she could move and attack two times, move 2 times and attack, move three times or move and activate her Viper AND take an action (using a skill card or chorum card, if she is president, for example).
Lee Adama's other special ability lets him kinda teleport into a Viper being launched and take one action (i am a little unsure of the timing, but I think his action takes place before the active player can do anything else), so you if launch one and the Lee player decides to jump into that Viper, you can no longer use your second "activation" on it.
Edited by Barl, 06 November 2014 - 04:37 PM.