VIDEO: 100 drones light up the night sky over Prague

One hundred drones took to the night sky above Prague's Vltava river earlier this month for a special show that recreated the Czech flag and other imagery in front of Prague Castle. The drone production is touted as the first of its kind in the Czech Republic.

Due to safety protocols, the project took place without spectators, and video from the show was only later published online.

Flying in unison with multi-colored light displays, the drones took off from a base at Prague's Dětský Island and swarmed above the Vltava river to recreate the Czech flag, a Czech lion, and an outline of the Czech Republic.

Planning the complex setup took an estimated 1,000 hours according to Spectrum Production, the company behind the drone show. The entire production lasted just nine minutes, but took months to coordinate.

At one point, the drones spelled out #silnější (#stronger), a reference to the Czech Republic's ongoing fight against the coronavirus pandemic.

"An integral part of the show was encouragement in these difficult times, that we can handle it and we can be stronger," said Spectrum's David Zaorálek.

The drones were equipped with LED diodes and each weighed about one kilogram. Instead of being flown by human pilots, the entire show was coordinated through a computer program.

The drone show took place on April 6 above Dětský, Střelecký, and Slovanský islands in the center of Prague.

"The show is pre-programmed and controlled by a computer, but for safety reasons there is also a crew who manage everything on site," Zaorálek adds.

"We monitor all parameters, even during the flight. The system has several levels of protective elements to prevent damage and falls."

According to Zaorálek, dozens of permits had to be obtained for the show, from the city of Prague as well as the Czech Republic's Civil Aviation Authority. The drone pilots who operated the show also needed to be licensed.

Because the drones could only fly in good weather, Spectrum also needed to monitor forecasts and plan around strong wind or rain.