From Halopedia, the Halo wiki
Ryan Frank was the pilot of Pelican 653, a D79 dropship assigned to the UNSC Infinity. After Fireteam Crimson's search for Spartan Gabriel Thorne in the area know as the "Quarry" was unsuccessful, Robert Dalton ordered Pelican 653 to extract them. Shortly after arriving the Pelican was destroyed by Covenant reinforcements and Frank was killed.
Although all Air Force combat pilots must be commissioned officers, in-game text identifies Frank as an Airman (E-2). This likely stems from the assumption that "airman" is a generic term for pilots or Air Force personnel in general, rather than a specific rank.
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