TH8 - 2 Lightning Spells Lv5 + 1 Earthquake = 1 Air Defense Lv6

Dragons attack with 3 lightning spells are very popular TH7 and TH8 strategy for a long time among Clash of Clans players. You can take down 1 air defense with 3 lightning spells, but no spell left after that.

Now it's more difficult to use the technique since CoC introduced new defense: Air Sweeper. But with new dark spell called Earthquake, you still can take advantage from this strategy with a little bit modification.

You can use only 2 Lighning Spells + 1 Earthquake (any level) to take down up to air defense lv6. So you still have more space for Rage Spell or Heal Spell, depends on your strategy.

Below is an example how to attack with full dragons, 2 lightning spells, 1 rage spell, and 1 earthquake. Watch out!

More examples:

Update: October 04, 2015
6 stars in clan war with Christopher (Dragon Master)