No shots were fired. No one was injured. The robbery was over within minutes. That told, and eight hooded thieves have just pulled off what could be one of the biggest $50 million worth diamonds heist in a lifetime.

The gang knew it was all a matter of precision timing for them to get what they came for. And they did so quite marvelously in one grand sweeping fashion.

On Monday night, a Zurich, Switzerland-bound flight LX789airplane was meant to take off at 8:05 p.m. But it was not just a regular ho-hum airplane doing its usual routinary transport of travelers. It carried a far precious cargo - diamond jewels worth tens of millions of dollars.

And before 8pm, just when the precious diamond jewels had been loaded into the aircraft and just about when it starts to move, in came two vehicles with police-like markings, likewise equipped with blue police lights, with occupants dressed in police uniforms. To the common folks, it looked like there would be a raid.

The vehicles forced their way through airport's security barriers, sped towards the passenger aircraft which is about to take off on the runway, calmly ordered ground staff workers and the pilot to back off as they unload the gem-filled packets from the cargo hold, got as much as they can, and then sped again and exited through the same gap they had made in the security barriers.

All happened within less than five minutes.

"They were very, very professional," Ine Van Wymersch, Brussels prosecutor, said.

Caroline De Wolf, a spokeswoman for the Antwerp World Diamond Centre (AWDC), said the gang's precision timing did not just happen by chance. There was very careful and detailed planning involved.

"There is a gap of only a few minutes between the loading of valuable cargo and the moment the plane starts to move," she said. "The people who did this knew there was going to be this gap and when."

That the group had access to inside information "is an obvious possibility," Ms Van Wymersch said.

The stolen precious diamond jewels, a mix of rough and polished stones, bore a declared value of about $50 million, according to AWDC. But the aviation-security specialist said the jewels could be worth up to $350 million.