ALL ships in UFO can be shot down with Plasma-cannon from an Interceptor w/o exposing the fighter to enemy fire... besides from the battle-shit..
2 different tactics regarding them...
either you "swarm" them with 3-4 interceptores, armed with plasma or even better, fusion-balls
OR
you only take on the ships when they have landed or attack them with Firestorm/Avenger-crafts armed with fussionballs/plasma..
nr 1 WILL ressult in many/all crafts are lost.
nr 2 often ressults in 1 or more craft beeing grounded for a looooong time repairing (we'r talking up to 20 days here)
Funnies thing ever done: Shooting down a Battle-shi with CANNON..
Was bored.. armed 6 Avengers with cannons, and sent em up..
After empteing over 2.000 shells into the poor Ufo, it crashed..
Also.. if you'r beeing plauged by base-assult attempts.. here is a hint..
Arm the base to it's teeth with your best men, and JUST the equipment they need.. sell your Gravsheild and save 4 fussion-defences..
Next attack minght get throu.. kill them in the base..
Now.. for this to work, you should have a mind-shield in the base up and running..
After the attack, the aliens seems to "forgett" the location of the base..
They start over searching for it (small scout, large scout, battle-ships; all tagged Alien retalliation)
Take them down nice and calm.. this will keep the base clean, and free up space for better buildings then defence.. just keep minimal defence (5 fussion and 1 gravshield will repell 19 of 20 attacks).