Just clarifying a couple things up:

1. Midgardsormr went inactive after the fight in Sigmascape, having used up all his energy to free the Warrior of Light from Omega.

2. Midgardsormr did not go on a suicide mission against the Imperial air force. It wasn't even a mutual kill. Midgardsormr actually defeated the Agrius; were it not for his prideful desire to show off by coiling around it and roaring, he would have been fine - it was the ceruleum tanks exploding shortly post-victory (while he was coiled around the ship) that did him in.