The flight time from Shenzhen to Singapore is 4 to 6 hours or even longer. The flight time depends on the specific route, aircraft type and flight speed of the flight. Shenzhen Airlines flight ZH9023 took 5 hours and 9 minutes. There are also flights with a flight time of more than 6 hours. Singapore Airlines flight SQ847, flight time 1 1 hour 50 minutes.

Seriously, the above answers are for reference only, and the actual flight time will be affected by many factors, including weather, air traffic control and aircraft maintenance.