Why do Quebec inmates keep flying out of prison? How do you stop them?

A helicopter lands in a prison courtyard, picks up a trio of alleged gangsters and flies away.

“It seems like it’s out of a movie. It’s very unusual,” said Colin Lobo, head of Lobo Consulting Services Inc., a company that designs and assesses security systems for justice facilities.

Not that unusual: This is the second helicopter jailbreak Quebec has seen in as many years.

In March 2013, two inmates made a similar attempt to escape in Saint-Jérôme Que.

Then, a helicopter pilot was forced at gunpoint to fly to the prison on a Sunday afternoon. Two inmates at the facility, about 60 kilometres from Montreal, climbed a rope ladder into the hovering helicopter and fled.

The two escapees and the two men accused of hijacking the chopper were picked up by police in Mont-Tremblant, about 85 kilometres away, within a few hours of the escape.

In this case, however, the three men who absconded via helicopter from Orsainville Detention Centre near Quebec City are still at large – Interpol has issued an international alert for their recapture; Quebec Premier Philippe Couillard has ordered an internal probe of these helicopter escapes.

READ MORE: Infamous helicopter prison escapes

It could be – at least in part – an architecture issue.

Lobo says an open courtyard can pose a security risk in detention centres.

“Traditionally, correctional facilities had a large outdoor courtyard that was outside of the main building.

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These courtyards were protected by a wall around the yard. However, this makes the yard more susceptible to security risks such as helicopters and contrabands,” Lobo said.

“Newer facilities have moved away from this approach and the outdoor yard is part of the entire building with a smaller opening for fresh air and natural light”.

Lobo says staying away from scheduled routines is another one way to prevent similar breakouts.

“When there is no exact routine, it becomes more difficult for an inmate to plan and coordinate with their counterparts on the outside. … The number of officers and locations of the officers when inmates are within the yard also plays a vital role.”

The accessibility of outdoor prison courtyards from the air could also be a factor in drug drops a Quebec corrections officer earlier claimed happen all the time.

The missing inmates – Yves Denis, 35, Denis Lefebvre, 53, and Serge Pomerleau, 49 – were originally arrested on drug trafficking and gangsterism charges in 2010, police say.

Denis is also facing first-degree murder charges. Lefebvre and Pomerleau are facing charges of murder and conspiracy to murder, according to the Quebec provincial police website. They were supposed to have a court date Monday.

According to court documents, Lefebvre allegedly supplied a helicopter to help with a planned (but never executed) robbery from a Val d”Or mining company, the Montreal Gazette reported this week.

Deputy Premier Lise Theriault said security restrictions against the three men were eased just a day before their daring getaway.

Theriault said a judge granted a request by the trio on Friday to have more flexible detention conditions, including the possibility they no longer be obliged to wear handcuffs.

The minister said she doesn’t know why the judge agreed to the request.

The spectacular escape dominated question period in the National Assembly this week, with Theriault peppered on the subject for more than 30 minutes.

With files from the Canadian Press.