The bandit fires at them head on...
Why do Mav and Rooster spend the last of their flares to defend against that missile? It seems to me that was a mistake on their part. Using any flares in that situation would be unnecessary and a waste of their last flares.
I dunno, it seemed to work.
They fired the flares and pulled up. Instead of course-correcting to hit them head-on, the missile went right for the flares.
The way I saw it, they fired the flares as they dodged-flipped the oncoming missile.
The flares got the missile as they had already successfully dodged. Just seemed redundant and unnecessary in hindsight...
But I can chalk it up to a error on the characters in the heat of battle, not the production and writing.