A test this summer in the Baltic Sea east of Stockholm will begin to define the future for the exponentially growing, crowd-sourced, global surveillance network that goes by the name of Flightradar24.

The service that started on a lark—with one Kinetic Avionics Automatic Dependent Surveillance-Broadcast (ADS-B) receiver in 2006—now covers about 80% of the world’s landmass with 6,200 receivers, expanding at the rate of 50 new receivers installed every week, and is the largest among a growing number of privately owned aircraft surveillance networks. The receivers, many provided at no cost by Flightradar24 and placed at homes and businesses of ardent supporters, capture the 1-sec. position and identification outputs from ADS-B avionics now on an increasing number of airliners, business jets and most other aircraft. About half of the receivers today also track aircraft carrying legacy “Mode S” transponders using a form of triangulation called multilateration.

Even when practically all of the Earth’s landmass has coverage, a feat Flightradar24 hopes to complete this year, co-founder Mikael Robertsson points out that roughly 70% of the globe—the oceanic domain—will still be largely in the dark when it comes to surveillance, even with stations placed on as many islands as possible. His company plans to play a prominent role in the race to open up the oceans to low-cost tracking of aircraft, and a search for potential solutions starts in part with the Baltic Sea test. “Our goal is now to cover the world,” says Robertsson.

Speaking to Aviation Week in New York in late January, Robertsson was scant on details but said the test will look at the performance of ADS-B receivers attached to buoys, a relatively low-cost solution the company could fund on its own. If successful, the test could lead to fleets of buoys in captive locations throughout the oceans or left to slowly free-float on the currents between continents. Other technologies under consideration include balloons and space-based receivers. Robertsson says the company is talking with “one partner” about space-based systems. He confirms that partner is not Aireon; that company plans to go live in 2018 with a network of space-based ADS-B receivers funded by a group of air navigation service providers.

For many other companies, such a lofty goal might be eyed with suspicion, but given the meteoric rise of the passive surveillance network, fueled by two co-founders with no insider experience in the aviation industry, Flightradar24’s plans may hold water.

Robertsson and Olov Lindberg happened upon the idea for a flight-tracking company after developing and launching an airline price comparing website, Sweden’s version of Kayak, in 2006. “We became the biggest price-comparison site in the Swedish market in just one year,” says Robertsson. They bought the Kinetic ADS-B receiver to play around with and decided to post screen shots generated by the receiver’s software updated every 60 sec. as a free subpage to their Svenska Resenätverket AB price comparison website, called Flygradar, starting in 2007. He and Lindberg sold the price-comparison site in 2014.

At the time, Robertsson estimates that 40-50% of the aircraft overflying their Stockholm location were equipped with ADS-B. “We made [Flygradar] just to get more traffic into the price-comparison site, but then the subpage became more popular than the [main site], so we registered a separate domain—Flightradar24,” he says. At the start, Robertsson and Lindberg had contacted enthusiasts around Europe who already had their own receivers, sending them software that would upload the tracking data to Flightradar24’s servers. They launched the new site in 2009 with “eight or nine” receivers connected to that server. In 2010, they published their own applications with data plotted using Google maps. 

The idea caught on quickly, with owners of more receivers contacting them for a copy of the software. In less than six months, Robertsson says, the whole of Europe was covered. The timing was fortunate. In April 2010, the Eyjafjallajökull volcano erupted in Iceland, cutting off air traffic and sending onlookers to Flightradar24 to get the big picture. “They showed our map on CNN and BBC, and all the biggest news channels were using our maps,” says Robertsson. The interest generated web hits—4 million in one day in April 2010. “That’s when we understood that this was more than a hobby project,” says Robertsson. Network expansion accelerated and by 2012, Robertsson and Lindberg hired former Lindberg classmate and Internet entrepreneur Fredrik Lindahl as the CEO to split Flightradar24 into a separate company.  

There were 500 receivers in the network, and the company had just signed an agreement with German electronics manufacturer Gunter Kollner Embedded Development to produce its own branded receivers. “In less than three years since then, we went from 500 to 5,500 receivers,” says Robertsson. Those receivers cover practically 100% of Europe and North America, all of Japan, and 80-90% of South America. Growing fast is coverage in Asia, Russian, India, Pakistan, the Middle East, Thailand and Malaysia, he says. 

China has been more problematic, with the country essentially barring the service by blocking an essential ingredient—Google maps. He says Chinese search-engine provider Baidu launched “a copy” of Flightradar24 a few months ago using flight-tracking data from within the country. “They don’t have issues with the data itself, it is more that they want to do it by themselves and not have a Western company doing it for them,” he says of a surveillance service. Regardless, Robertsson says contacts are in place to get more of China covered this year, potentially with alternatives to Google maps. 

Africa, by contrast, has been problematic because of power interruptions. Robertsson says whereas globally about 90% of receivers are operating at any given time, in Africa the number is 25%. “We are investigating all options [for Africa],” says Robertsson. Included are satellite-based Internet and solar panels and wind energy to keep the receivers powered. The company is also studying a next-generation ADS-B receiver with integrated antennas.

Privacy advocates will be pleased to know that Flightradar24 charges no fees to block the tail numbers of business jets based on an internal list of aircraft types the company put together, as well as the FAA’s list of blocked tail numbers, and direct requests from operators.

The cost of shipping 50 new receivers a month, at $400-500 each, eclipses the salaries of the small staff, says Robertsson. Even so, the company has been profitable through a combination of advertising, IOS (Internetwork Operating System) and Android application sales and premium service on the website. Revenue from one-time application downloads continues to rise, in part when customers switch between phone platforms, and new apps are being built, but the company is putting more resources into new options for the web version, for which subscribers pay a monthly fee. The current rate for the single “premium” option is $2.99 per month paid one year in advance. There is a free Web service, but it has advertisements and times out after 15 min. Robertsson says the company has a “very, very long road map” for new features for both the apps and the web pages, as well as “quite a big update” for the Web in April;  there will be four different premium levels.

Despite profits, the Flightradar24 is exploring new business-to-business models. “The company has been 100% funded by me and Olov, and it has been profitable since Day One,” says Robertsson. “But it is not a good business model. People buy the app for $3 and some people bought it 3-4 years ago and we do not get any more money from that.” As of mid-February, Robertsson says, the company had sold 3-4 million applications and was honoring 10-15 “free ups” on the Web, with the numbers of both growing.

Potential B2B paths could include more licensed sales of data to airlines, an option that three major non-U.S. airlines use in their operations centers, but one that Robertsson says is not profitable today. “It could be our future, but today we have only a couple of them,” he says. “It does not even cover the cost of selling [the data].” Competitor FlightAware, which is now building its own network of receivers, has teamed with both SITA and Rockwell Collins as a data provider for the companies’ surveillance and data services for airlines and business jets.

To the broader question of quality control for a crowd-sourced surveillance system, Robertsson says about 95% of the receivers sent out come online and about 90% remain online. Hosts are granted free access to the premium service offering. “The incentive for most people is just better coverage. That’s enough for most people,” he says. 

Better coverage also stems from the increasing number of receivers with multilateration capability to track non-ADS-B-equipped aircraft. Health of the ground network is monitored by a team of five employees who have a “daily routine.” If a receiver goes down for more than 6 hr., an email is sent to the host asking about the problem. After 72 hr., an email goes to customer support, and they try to contact the host. Those contact attempts continue for two weeks. “If the receiver is not online after one month, we ask the host to send it back,” says Robertsson.

“Most” airlines use its website or applications in some form or other, and the Web page has been tracked by IP address to airlines or has been spotted in the operations centers or in promotional videos for dozens of airlines, Robertsson says. On EasyJet’s website recruitment page, “they [feature a] guy sitting at desk working on Flightradar24,” he says. “It feels good that they have a tool that they can track their aircraft with.”

However, it has proven difficult to monetize that affection. Robertsson says his company has reached out to “many, many” airlines with samples of B2B products, only to be turned down due to cost considerations. “We say $1,500 per month and they say, ‘No chance—we’ll never pay $1,500 if we can get it for free on the net.’ Then it’s not so fun.”

Another hindrance is Robertsson and Lindberg’s lack of an aviation background. They have not used the tracking tools airlines use nor do they know what systems are popular. That is both a plus and a minus, says Robertsson. “If you’re used to using a tool and start a new company, then maybe you try to make a copy of the tool you used in a previous company. But here we [have a clean slate], so we are creating something new.”  

Editor's Note: This article was edited to correct some inaccurate figures, a transponder type and the name of the Chinese entity that launched "a copy" of Fligthradar24 in China.