According to the Phys.org article NASA flies large unmanned aircraft in public airspace without chase plane for first time:

Flights of large craft like Ikhana, have traditionally required a safety chase aircraft to follow the unmanned aircraft as it travels through the same airspace used by commercial aircraft. The Ikhana flew in accordance with the Federal Aviation Administration's (FAA) Technical Standard Order 211—Detect and Avoid Systems—and Technical Standard Order 212—Air-to-Air Radar for Traffic Surveillance.

[...] The Ikhana aircraft was equipped with detect and avoid technologies, including an airborne radar developed by General Atomics Aeronautical Systems, Inc., a Honeywell Traffic Alert and Collision Avoidance System, a Detect and Avoid Fusion Tracker, and an Automatic Dependent Surveillance-Broadcast capability – a surveillance technology where the aircraft determines its position via satellite navigation and periodically broadcasts this information so other aircraft can track it.

The flight took off from Edwards Air Force Base in California and entered controlled air space almost immediately. Ikhana flew into the Class-A airspace, where commercial airliners fly, just west of Edwards at an altitude of about 20,000 feet. The aircraft then turned north toward Fresno, requiring air traffic control to be transferred from the Los Angeles Air Route Traffic Control Center to the Oakland Air Route Traffic Control Center. On the return trip, the pilot headed south toward Victorville, California, requiring communication control to be transferred back to Los Angeles.

During the return flight, the pilot began a gentle descent over the city of Tehachapi, California, into Class E airspace—about 10,000 feet—where general aviation pilots fly. The pilot initiated an approach into Victorville airport at 5,000 feet, coordinating in real time with air traffic controllers at the airport. After successfully executing all of these milestones, the aircraft exited the public airspace and returned to its base at Armstrong.

"We are flying with a suite of sophisticated technology that greatly enhances the safety capabilities of pilots flying large unmanned aircraft in the National Airspace System," said Scott Howe, Armstrong test pilot. "We took the time to mitigate the risks and to ensure that we, as a program, were prepared for this flight."

Tuesday's flight was the first remotely-piloted aircraft to use airborne detect and avoid technology to meet the intent of the FAA's "see and avoid" rules, with all test objectives successfully accomplished.

At the end of the article:

More information: For more information on NASA's Unmanned Aircraft Systems Integration in the National Airspace System project, visit go.nasa.gov/2sx9VCn.

Question: While this was the "...first remotely-piloted aircraft to use airborne detect and avoid technology to meet the intent of the FAA's 'see and avoid' rules, with all test objectives successfully accomplished", (without a chase plane?) how rare is it for remotely-piloted aircraft to fly through US airspace where commercial or general aviation also flies without all those extra qualifications? Has this happened several times, several hundred, daily? Is it even more infrequent without a chase plane?

enter image description here enter image description here

Click images for full size.

above left: "Aircraft maintenance crews at NASA‘s Armstrong Flight Research Center prepare the remotely-piloted Ikhana aircraft for a test flight June 12, 2018. The test flight was performed to validate key technologies and operations necessary for the Federal Aviation Administration's approval to fly the aircraft in the public airspace without a safety chase aircraft." Credit: NASA/Ken Ulbrich

right: "NASA’s remotely-piloted Ikhana aircraft, based at the agency’s Armstrong Flight Research Center, is flown in preparation for its first mission in public airspace without a safety chase aircraft." Credit: NASA/Carla Thomas

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    $\begingroup$ The military has been doing it for decades - they just don't tell anyone. $\endgroup$
    – jwzumwalt
    Commented Jul 28, 2018 at 17:38
  • $\begingroup$ note: edit was me, I forgot to log in so it shows as anonymous user. $\endgroup$
    – uhoh
    Commented May 17, 2021 at 21:01

2 Answers 2


In the US, the main operators of large UAS (i.e. non CFR Part 107 aircraft) are Air National Guard (MQ-9) and the Department of Homeland Security (Customs and Boarder Protection, also MQ-9). Here is a table from the Pentagon on how many missions UAS flew domestically in FY2018. (Note that these are "missions" and do not include other types of operations such as training or flight test, see below.)

enter image description here

A report from OIG published in 2014 lists a total of 5,102 flight hours by CBP in FY2013 (which is supposed to be closer to 26,000+, hence the OIGs investigation). Air National Guard also operates MQ-9 domestically for frequent training missions and contractors such as General Atomics Aeronautical Systems, Inc. and Northrop Grumman operate a fleet of capital aircraft at their respective training centers (e.g. Grand Forks). Lastly, of course, NASA also flies UAS. An example of how such missions are executed is described in this NASA report on the Western States Fire Missions starting on page 30.

So on your question about frequency: Assuming that the sum of all those aircraft result in ~5x number of flight hours, you'd be looking at something like 25,000 yearly flight hours in the US National Airspace System of large Remotely piloted aircraft. This is likely on the low side given the OIGs observation about the operational tempo of the CBP fleet.

So Why Is This Demonstration Relevant?

You may ask: if we're already operating these aircraft without chase planes, what was so special about this flight? It was the ability to fly a UAS without a chase plane without first having to climb to Class A airspace.

FAA Notice 8900.227 stipulates the requirements for how to obtain operational approval for an unmanned aircraft; specifically, it states:

... compliance with the see-and-avoid requirement [is a] primary concerns in UAS operational approvals leading to [...] the use of observers [to maintain] flight separation and collision avoidance or ‘segregation’;

In the case of a flight with a chase aircraft, that visual observer is onboard the chase aircraft. This is also where the "Visual Line of Sight Requirement" comes from - the observer/pilot must be able to see the aircraft during the operation. There is one exception in N8900.227 for the visual observer (VO) requirement:

VOs are not required in Class A airspace [...]

As a result, so far operations of the above-mentioned agencies occur almost exclusively in Class A airspace; i.e. above 18,000ft. Since those entities are either government agencies or contracting with a government agency, access to restricted airspace is straight forward where these aircraft can circle up or down to and from Class A airspace. In the case CBP and Global Hawk operations in Grand Forks there is a Temporary Flight Restriction that enables this access to Class A airspace without the need of a chase aircraft below 18,000ft.

This type of operation is incredibly inefficient though (imagine if manned aviation had to operate like that). As a result, and that is what makes this NASA flight unique, the ability to use an onboard system to detect and avoid other aircraft (i.e. a Detect and Avoid System) when operating in airspace other than Class A, in particular Class E below 10,000ft where "non-cooperative" aircraft operate removes a list of operational limitations. From N8900.227 again:

b. Risk Mitigation. While considerable work is ongoing to develop a certifiable detect, sense, and avoid system as an AMOC with the see-and-avoid aspect of §§ 91.113 and 91.115, no current solution exists.

The "considerable work" mentioned refers to this NASA project - and the flight was the capstone demonstration to show equipment in fact can serve as an Alternate Means of Compliance (AMOC) when operating outside of Class A airspace.

  • $\begingroup$ Thank you very much for such a thorough answer, and for identifying the more significant and underlying question So Why Is This Demonstration Relevant? (or newsworthy) $\endgroup$
    – uhoh
    Commented Feb 13, 2019 at 1:29

To answer the latter part of your question according to FAA regulations no UAS' may fly out of line of sight or without a chase plane:

Flights below FL180 must have a dedicated observer. These duties may be performed by a ground based observer or chase plane.

So in according to the legislation it never happens, at least not regularly. You can get a waiver from the FAA to bypass this as is outlined in this question.

Its hard to say how often this happens with chase planes as there is nothing against the regulations on it and there may not be much in the way of reporting when it happens. This podcast discusses some of the sub scale testing NASA does and according to the engineer being interviewed they are only flying a test airframe once every few months. You can find a nice listing of the various tests and things that NASA is up to here.

Most notably NASA has been using some old globe hawk drones to monitor hurricanes off the cost of Florida. It does not seem this is a regular occurrence and its unclear in what airspaces it flew.

The answer boils down to not all that often.

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    $\begingroup$ That darn NASA; next thing you know they'll be trying to putting things in outer space without pilots! $\endgroup$
    – uhoh
    Commented Feb 9, 2019 at 4:23

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