Two Toronto teens who launched a Lego man into space were rewarded with some awe-inspiring video, but experts say anyone trying to replicate the feat should be aware of air safety.

The Grade 12 students say they used a helium-filled weather balloon and a makeshift Styrofoam box to send the tiny plastic figure about 24 kilometres into the air.

Cameras attached to the box captured the Lego man's amazing journey on video, which was later posted on YouTube.

Mathew Ho, 17, says he and his friend did some online research to make sure they were informed about the proper use of weather balloons and weren't doing anything dangerous or illegal.

A spokesman for the Air Canada Pilots Association who viewed the balloon launch video says it shows a "tremendous degree of resourcefulness" on the part of the teens.

Capt. Barry Wiszniowski, chairman of the pilot group's flight safety division, says the biggest concern would be a lack of notification to the users of air space.

Impact could be similar to bird strike

Most weather balloons are launched from known sites, Wiszniowski said. If other balloons are being sent up, it could pose a concern to aviation.

"I think in the 25 years that I've been flying I've seen two weather balloons that passed on one side of the aircraft or the other," he said.

A pilot might not have enough reaction time if such a balloon popped up unexpectedly, he added. With the speed of a plane at altitude, the impact could be similar to a bird strike and could cause damage, especially if something was sucked into an engine, he said.

A spokesman for Transport Canada said in an email that small unmanned balloon flights are not governed by the Canadian Aviation Regulations.

But Transport Canada should be informed ahead of any such launch to ensure aviation safety is not threatened, said Kelly James.

"Aviation safety is the primary consideration and if Transport Canada feels that the launch of a small unmanned balloon poses a hazard to aviation safety, the department will co-ordinate with appropriate authorities as necessary," the email said.

Factors considered would be the date and time of launch, the size and number of balloons and proximity to airports, among other things, it added.

Contact authorities first

Ho advises anyone wanting to launch such a balloon to contact local authorities first.

"There's a lot of zoning bylaws on launching weather balloons," he said Friday. "You always have to be cautious…because there are overhead planes."

Ho and Asad Muhammad, also 17, used a cellphone with a GPS device to locate their spacecraft after it landed about 120 kilometres away from the launch site.

The pair conducted the flight as a hobby, Ho said, adding he was happy they could share the images that came back. But he said having an idea is one thing — making it work is the hard part.

"You have to put your ideas into motion and get working," he said. "Dream big and you never know what's possible."