China Eastern has grounded its fleet of 737-800s, state media reported. It is the country's sixth-largest operator of the type, with 89 planes, IBA said, but other Chinese carriers are continuing to fly the jets and China Eastern has not grounded its similar but slightly smaller 737-700s.

Jefferies analysts said China's aviation regulator was unlikely to ground the 737-800 fleet unless it specifically suspected a technical failure as the root cause because of the operational consequences of grounding more than 1,000 planes in the world's second-biggest domestic aviation market.

However, there are concerns the Chinese public could look to avoid flying on 737-800s until the cause of the crash is determined, given the broader reputational issues with the 737 family caused by the MAX, Cowen analyst Cai von Rumohr said in a note.

"Hence, isolating the cause of the crash will be critical," he added, noting the leading causes of commercial air transport crashes tend to be maintenance issues, pilot error or sabotage, rather than manufacturing or design issues.

The location where the descent from 29100 feet was initiated, coincides with the point where flight MU5735 began its descent (also from 29100 feet), the day before the accident.