Niniek Karmini, Jakarta – An Indonesian passenger jet was flying at up to 265 mph, almost double the normal landing speed, when it crash-landed one month ago, killing 21 people, a chief investigator Saturday.

A preliminary accident report has not yet determined, however, if pilot error caused the Boeing 737-400 to overshoot the runway, skid into a rice field and burst into flames at the Yogyakarta airport, Marjono Siswosuwarno said.

"The plane was flying well above the normal landing speed of 140 knots (160 mph) when it crash-landed," he said, putting the speed as it approached the runway at between 255 mph and 264 mph. "We are still interrogating the pilots to figure out why this happened... we haven't determined yet if it was pilot error."

Aviation experts confirmed that speed and flap warnings would have sounded in the cockpit and the pilot should have aborted the landing, according to The Sydney Morning Herald, which said it obtained a copy of the confidential Transport Safety Committee report.

It claimed the airport runaway also did not meet international safety standards – with a safety run-off a quarter of the recommended length – and that weather was good despite claims by pilots of a serious downdraft.

The March 7 crash was the fourth accident involving a commercial jetliner in Indonesia since 2005. Experts say poor maintenance, rule-bending and a shortage of properly trained pilots may contribute to the sprawling country's poor aviation safety record.

On Saturday, a privately owned, propeller-driven Cessna 172-P crashed on the outskirts of Indonesia's capital during a training flight, injuring three people onboard, two of them critically, police and witnesses said.