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]

[0] https://theaviationist.com/2016/07/18/exclusive-all-the-deta...

[1] https://www.theguardian.com/world/2016/jul/18/military-coup-...