They weren't sure it was him. Puts it in perspective that the military pilots would be averse to shooting down a civilian passenger jet. See here:
>TC-ATA [Erdogan's jet] used a callsign THY 8456 to disguise as a Turkish Airlines airplane (Turkish’s callsign is THY) [0]
>The jets didn’t fire after the presidential plane’s pilot told the fighter jet pilots over the radio that it was a Turkish Airlines flight, a senior counter-terrorism official told the Guardian. [1]