When I first heard it I thought maybe it was the freighter flight. After asking a few colleagues in the UAE, the airspace is quite congested over there and this was the result to avoid call sign confusion on the radio.
Most of the time airlines will append the letter D on the end of the call sign to denote that it’s the delayed service. This is handy when it’s flying close to the scheduled service.
Good Luck on the RPL.
