Google is launching balloons into near space to provide internet access to buildings below on the ground.
About 30 of the superpressure balloons are being launched from New Zealand from where they will drift around the world on a controlled path.
Attached equipment will offer 3G-like speeds to 50 testers in the country.
Access will be intermittent, but in time the firm hopes to build a big enough fleet to offer reliable links to people living in remote areas.
It says that balloons could one day be diverted to disaster-hit areas to aid rescue efforts in situations where ground communication equipment has been damaged.
Trying to simultaneously navigate thousands of the high-altitude balloons around the globe's wind patterns will prove a difficult task to get right.
Google calls the effort Project Loon and acknowledges it is "highly experimental"
What are superpressure balloons?
Superpressure balloons are made out of tightly sealed plastic capable of containing highly pressurised lighter-than-air gases.
The aim is to keep the volume of the balloon relatively stable even if there are changes in temperature.
This allows them to stay aloft longer and be better at maintaining a specific altitude than balloons which stretch and contract.
In particular it avoids the problem of balloons descending at night when their gases cool.
The concept was first developed for the US Air Force in the 1950s using a stretched polyester film called Mylar.
More recently, Nasa has experimented with the technology and suggested superpressure balloons could one day be deployed into Mars's atmosphere.
Each balloon is 15m (49.2ft) in diameter - the length of a small plane - and filled with lifting gases.
Electronic equipment hangs underneath including radio antennae, a flight computer, an altitude control system and solar panels to power the gear.
Google aims to fly the balloons in the stratosphere, 20km (12 miles) or more above the ground, which is about double the altitude used by commercial aircraft and above controlled airspace.
Google says each should stay aloft for about 100 days and provide connectivity to an area stretching 40km in diameter below as they travel in a west-to-east direction.
The firm says the concept could offer a way to connect the two-thirds of the world's population which does not have affordable net connections.