Commercial airliners do transmit some information: radio transponders identify them when scanned by radar, and many are fitted with an Aircraft Communications Addressing and Reporting System, or ACARS, which periodically relays text-message like snippets of information about the aircraft’s status. In the case of Flight MH370, the transponder seems to have stopped transmitting, and the airline has reportedly declined to comment about ACARS signals while the incident is being investigated.

But black boxes record much richer flight data, including pilot voice communications. So why can’t this be sent to the ground? It’s not a new idea: more than a decade ago, computer scientist Krishna Kavi, now at the University of North Texas, proposed streaming this data to cloud storage, in a system he dubbed the “glass box.”

The main objection has been the bottom line. Transmitting data through satellites isn’t cheap, and if such a system were operating continuously, the cost would be prohibitive. In 2002, L-3 Aviation Recorders of Sarasota, Florida, estimated that a U.S. carrier with a global network would need to spend $300 million a year to stream all its flight data in real time.

L-3, which is the leading manufacturer of black boxes, clearly has a stake in the status quo. What’s more surprising is that its analysis has been widely accepted by industry experts and media commentators — in its reporting on Flight MH370, for instance, Wired claimed it would cost “billions of dollars” to implement flight data streaming across the airline industry.

That’s only true if you accept L-3’s false premise that all flight data would need to be streamed, all of the time. “You don’t need to spend money on streaming terabytes of data from normal flights,” says Paul Hayes, safety and insurance director with Ascend, an aviation consultancy based in London, U.K. Instead, systems could be designed to be triggered by unusual flight events, and only then start streaming flight data.

This isn’t just a theoretical possibility: such devices are already on the market, fitted to around 350 planes run by about 40 operators. They just haven’t been configured to be a “virtual black box,” and are instead transmitting data that help airlines plan maintenance, or work out how to minimize fuel consumption. “The system is available, certified and in use,” says Richard Hayden, a director of FLYHT, the company that makes the system.

FLYHT’s basic product is known as the Automated Flight Information Reporting System. It transmits data via Iridium satellites — which also allow people to use a satellite phone from anywhere in the world — and can be programmed to start streaming flight data when a plane deviates from its flight plan, or instruments suggest something is going wrong.

Of course, that wouldn’t yield much information if a plane is blown out of the sky by a bomb, or suffers a sudden catastrophic structural failure at cruising altitude. But in those rare cases, conventional black boxes are really the only viable technology.