The signals would hop forward, from one balloon to the next, along a backbone of up to five balloons.
Google's balloons fly free and out of sight, scavenging power from card table-sized solar panels that dangle below and gather enough charge in four hours to power them for a day as the balloons sail around the globe on the prevailing winds.
The helium-filled balloons inflate to 49ft in diameter and carry transmitters that could beam 3G-speed internet to some of the 4.8billion people in the world that are not yet online, supplying an area of about 780 square miles - twice the size of New York City.
Far below, ground stations with internet capabilities about 60 miles (100km) apart bounce signals up to the balloons.
Nicknamed Project Loon, the internet giant is sending the superpressure balloons 12 miles up into the air, where they will sail around the globe at twice the altitude of aeroplanes.
Project Loon was developed in the company's X Lab by the same team behind Google Glasses and the driverless car. It is hoped it could save developing countries the high cost of laying fibre cables to get online and lead to a dramatic increase in internet access for the likes of Africa and south-east Asia.
Loon could even provide emergency back-up for areas during natural disasters.
This week the balloons, made from a thin polyethylene film, were released from a frozen field near Lake Tekapo on New Zealand's South Island, where they sailed past the magnificent Southern Alps mountains on their ascent.
'It's pretty hard to get the internet to lots of parts of the world,' Richard DeVaul, chief technical architect at Google, told the BBC.
'Just because in principle you could take a satellite phone to sub-Saharan Africa and get a connection there, it doesn't mean the people have a cost-effective way of getting online.
'The idea behind Loon was that it might be easier to tie the world together by using what it has in common - the skies - than the process of laying fibre and trying to put up cellphone infrastructure.'
Fifty volunteer residents signed up to be a tester for a project that was so secret no-one would tell them what it was for.
Technicians came to the volunteers' homes and attached bright red receivers the size of basketballs that look like giant Google map pins - which every building would need to receive the signal.
Charles Nimmo, a farmer and entrepreneur in the small town of Leeston, was the first tester to get online from the airborne balloons.
Mr Nimmo was able to spend about 15 minutes surfing the web before the balloon transmitting the signal sailed past.
His first stop was to check out the weather. He wanted to find out if it was an optimal time for 'crutching' his sheep, the term for trimming away the wool around a sheep's bottom.
Mr Nimmo is among the many people living in rural areas, even in developed countries, who cannot get broadband access.
After ditching his dial-up service four years ago in favour of satellite internet, he found himself stuck with hefty bills.
'It's been weird,' he said of the Google Balloon Internet experience. 'But it's been exciting to be part of something new.'
Project leader Mike Cassidy said: 'It's a huge moonshot. A really big goal to go after. The power of the internet is probably one of the most transformative technologies of our time.'
People have used balloons for communication, transportation and entertainment for centuries. In recent years, the military and aeronautical researchers have used tethered balloons to beam internet signals back to bases on Earth.
Before heading to New Zealand, Google spent a few months secretly launching between two and five flights a week in California's central valley.
'We were chasing balloons around from trucks on the ground,' said Mr DeVaul.
'People were calling in reports about UFOs.'
