Turkish Airlines Flight 981
ATC cleared the aircraft to 6,000 initially, then up to FL230 within 2 minutes of leveling off. Shortly after 1140 hrs, when Turkish Airlines flight TK981 had reached 12,000 (roughly 3,700 m) feet during climb, the Air Traffic Control recorded a transmission in the Turkish language, partly covered by heavy background noise and accompanied by the pressurization warning and then the overspeed warning; and at the same time, the aircraft radar return split in two and the secondary radar label disappeared.