From Indonesia National SAR official briefing:
(all times local)
05:36 QZ8501 departed Juanda airport, Surabaya
06:12 Contacts Jakarta center 125.70 at FL320, requests weather deviation left of M635 airway and climb to FL380
06:16 QZ8501 still observed on radar
06:17 Radar contact lost. Radio contact lost. Only ADS-B signal remained.
06:18 All contact lost. Only flight plan view on radar screen.
07:08 ATC declares INCERFA (aircraft position uncertain)
07:28 ATC declares ALERTFA (emergency alert)
07:55 ATC declares DETRESFA (emergency distress)