For an aircraft like China Eastern‘s Boeing 737-800 to crash in midflight is “simply unprecedented,” said one aviation analyst who cited the plane’s excellent safety record.

“Air travel is the safest form of transport. But when we do suffer incidents or accidents, we don’t see anything like what we have seen in China over the last 24 hours,” Alex Macheras, an independent aviation analyst, told CNBC’s “Capital Connection” on Tuesday. 

“This nosedive was simply unprecedented, especially from cruising altitude. We’re talking about the safest phase of the flight. That’s why those answers are going to be needed as soon as possible to determine,” he added.

No bodies or survivors have yet been found from the crash as of Tuesday morning, Chinese state media said.

The domestic flight was carrying 132 people when it nose-dived Monday afternoon in the southern region of Guangxi.

The plane was cruising at 29,100 feet and began a sharp descent after 2:20 p.m., recovering more than 1,000 feet briefly — then continuing to dive again before it lost contact. It fell more than 25,000 feet in about two minutes.

The 737-800 that crashed Monday in China first flew in June 2015. It was not a Boeing 737 Max, the plane that was grounded worldwide after two fatal crashes in 2018 and 2019. China was one of the first countries to ground the 737 Max after the second of the two crashes. 

“The aircraft involved was a 6-year-old, so a very young 737-800, which has a stellar safety record all over the globe,” said Macheras.

“We are talking about an aircraft that makes up the entire fleet of European low-cost airline Ryanair. An airline aircraft that is in service with American Airlines, Qantas, FlyDubai, Ethiopian, KLM,” he added, saying the plane is used to performing in very difficult conditions.

According to travel analytics firm Cirium, there are more than 4,200 Boeing 737-800s in service worldwide and 1,177 of them are in Chinese airlines’ fleets.

Chinese President Xi Jinping has ordered an investigation and rescue teams to the location of the crash in the rural, mountainous region.

Sheila Kahyaoglu, aerospace and defense analyst at Jefferies, said the safety record of the aircraft makes it highly probable something unusual happened during flight.

“Given the safety record of this aircraft, and the fact that it only had nine fatal accidents in 25 years, I highly doubt it’s a manufacturer’s issue,” she told CNBC on Tuesday.

“Obviously it’s too early to think about that, or to make that conclusion,” Kahyaoglu acknowledged, indicating that perhaps “something abnormal happened” since the aircraft has had a good safety record so far.

As the jet was a U.S.-made plane, the U.S. National Transportation Safety Board said it has appointed an investigator for the crash.

Investigators will work to recover so-called black boxes that contain cockpit voice recordings and flight data. They are also likely to examine the aircraft’s previous flights, maintenance history, weather data and pilot health.

Macheras said it’s the black box that is going to “ultimately push investigators into the right direction, in that quest for answers.”

“As the nature of the crash remains completely unexplained, what role the aircraft was playing will be the question on so many regulators’ [minds] worldwide,” he said. “There is always that risk and that’s why investigators will be wanting to rule out whatever they can. But as we say, the black box is what’s going to contain the most impact.”

— CNBC’s Evelyn Cheng and Leslie Josephs contributed to this report.