From Halopedia, the Halo wiki
When Jeffries joined the crew of the Midsummer Night, he and Finlay became fast friends; though shortly after, Jeffries was shot down by Insurrectionist AAA fire over Charybdis IX. Finlay's already-strong hate of Insurrectionists was fueled even more, making him very easily angered and aggressive. After the Midsummer Night arrived at The Rubble, Finlay was infuriated to learn that he and the rest of the crew were going to defend Insurrectionists even though they had lost many men to them in the past.
When Ignatio Delgado volunteered to be a pilot on the Midsummer Night, Finlay unleashed his anger against him (even though Ignatio was not really an Insurrectionist) and threw a punch in his gut. Delgado instinctively head-butted Finlay in the face. Surrounding pilots and an officer dragged Finlay away, and he was patched up by onboard doctors .
Later, during the Battle of Metisette, Finlay was aboard the first Pelican to be shot down by a Kig-yar anti-aircraft battery during re-entry into Metisette. The AA fire shattered his Pelican's tail, and caused it to spiral to the ground and explode .
He had a fervent hatred for Insurrectionists. Despite his fiery nature, he was renowned for his exceptional piloting skills with a D77-TC Pelican, the main dropship used by the United Nations Space Command. Though he reacted badly to Ignatio Delgado, Finlay's fellow pilots stated that Delgado could trust Finlay to have his back in the air, indicating that he was willing to put his issues aside while actually working with Delgado.
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