On TBolts, (and other fighters etc):-
- CAP uses up an early activation, which can be usefull to delay revealing what you intend to do,
- Intercept is a later activation that allows you to shoot down enemy a/c including enemy fighters and to lay BMs (both of which can give you air superiority)
Laying BMs on aircraft is almost as important as shooting them down. Working your aircraft within your own 'FLAK umbrella' (ie within 60cm of a Hunter) means that you can provide them some protection from the ground (or from other aircraft**). The same is true for ground troops. If you can, try to shoot at the enemy aircraft
once as they fly on and
once more as they fly away. Even if you do not hit them, you will lay two BMs that will make it much harder for that air formation to return the following turn. If you also intercept, you will lay a third BM (or a fourth etc) - - -
Always try to preserve your own A/c. Apart from Eldar, most a/c have poor armour, so position them where enemy AA cannot hit them. In the case of TBolts, you can stay at 30cm and still hit the target with rockets (and you might get lucky!). Also, don't forget fighters and Fighter Bombers can "Jink", so use it.
For any turn where you have 'air superiority' (where only your aircraft can fly over the battlefield), you can use the activation(s) to force the opponent to conform to your plans. This is done through supporting ground troops (prepping assaults etc), breaking formations and harassing broken formations. Up to a point, the more air power you have under these circumstances, the greater your chances of winning the game - through attrition if nothing else
(Note this is the main reason why air formations can become so powerfull - and why the 'air-game' can so easily unbalance E:A as a whole)** Remember that flying A/c already positioned on the table can also use their AA against any enemy A/c that ends their movement within range and arc of fire.