In an FCC filing, Google has told the US government that it believes its secret airborne network won't interfere with any existing networks and won't harm any people or animals. Google has been hoping to perform a "two-year nationwide test" of the network and recently addressed some concerns people had raised about it.

In the filing, Google only calls the project a "nationwide testing of airborne and terrestrial transmitters in the 71-76 and 81-86 GHz bands (collectively, the E-band)." It wants to keep the project a secret, but all signs point to it being for Project Loon, Google's airborne network of balloons which it has primarily tested in New Zealand. The application is signed by Astro Teller, the head of Google's "X" division, which houses Project Loon.

The "E-Band" that Google says it will use is often deployed as a wireless backhaul option for network providers. Fiber is, of course, preferable, but Fiber is expensive and sometimes—like in the case of Project Loon—you just can't use a wire. Most E-Band applications use highly directional antennas and are capable of multi-gigabit speeds over a mile or two. Google notes that it will have both terrestrial antennas that "will be pointed upward" along with airborne transmitters. In Project Loon, this would suggest the E-Band would be used for balloon-to-ground and balloon-to-balloon communication.

The current iteration of Project Loon uses LTE to provide service to users, basically making them flying cellular towers. Google doesn't have the nationwide spectrum to provide end-user LTE access itself, but that's not a problem since Google's current plan for Project Loon is to build the infrastructure and rent it out to existing telcos.

Some commenters had apparently worried that the RF energy from the balloons would or could harm people or animals (an odd concern, given that the E-Band has been in use for some time). Google said there was "no factual basis" for these concerns. There was also worry that an airborne E-Band transmitter could interfere with existing installations, but Google notes that thanks to the highly directional antennas, anything they're not aiming at would receive "only a small fraction of the maximum transmitted energy."

Google is still waiting for the test to be approved. The other concern for a nationwide Loon test would be the balloons falling out of the sky or interfering with an aircraft during launching and landing, but for that they'll need to talk to the FAA. Google already has permission to test the balloons in California and Nevada, and the company gives the local air traffic control a heads up when it needs to do a launch or landing.