A THY Turkish Airlines Boeing 737-800, registration TC-JHM performing flight TK-392 from Istanbul (Turkey) to Batumi (Georgia), was enroute at FL350 about 310nm east of Istanbul when the crew decided to divert to Ankara due to a cracked windshield. The aircraft landed safely at Ankara's Esenboga Airport about 80 minutes after departure. A replacement Boeing 737-800 registration TC-JGA reached Batumi with a delay of 4 hours. The occurrence aircraft returned to service after about 20 hours on the ground.