Are Military GPS Tests Threatening Airlines?

Are military GPS tests threatening airlines? The Global Positioning System simplified flying, not only for military aircraft but also for commercial planes. However, the system is not as safe as it was because attackers have become more intelligent and have access to modern jamming equipment.

So the military needed to upgrade its hardware to deter these attacks. And any upgrade requires tests before full integration.

So the question is, are military GPS tests threatening airlines? Let’s dive into this topic below.

Table of Contents

The Significance of GPS in Commercial Flying

GPS, originally Navstar, is a radio navigation system based on satellite data transmission that operates independently of any internet or telephone reception. The system provides navigation, timing, and position signals to any receiver on earth, provided there is an unobstructed line of sight from the receiver to at least four satellites.

Such a system is ideal for flying applications because it underpins the autonomous systems used by flight management computers and autopilot. So most airplanes feature ADS-B (Automatic Dependent Surveillance-Broadcast) transponders that use GPS signals to calculate the plane’s speed, heading, and altitude. This option is better than digital charts on tablets, which most private pilots use for their flights.

Two pilots in a plane’s cockpit

Two pilots in a plane’s cockpit

However, GPS is the property of the United States government. So the military can degrade the service or limit access selectively at any time.

Can GPS Experience Attacks?

Yes. And it can occur in two ways.


GPS jamming is an easy process. Satellites transmitting GPS data are 20,200 km or 10,900 nautical miles above the earth. So the power of the original signal is weak when it gets to receivers on the surface or airplanes. The average cruising altitude for airliners is about 10,000-12,000 meters (10-12 km), so they are way below the satellites in space, meaning the signal reaching their receivers is still weak.

A GPS receiver

A GPS receiver

Therefore, you can jam the system if you generate strong radio frequency signals that drown out the weak GPS signal. 

So the plane or ground-based receiver won’t be able to produce a geolocation result. This issue can be fatal when flying, especially during bad weather or poor visibility; pilots can crash into mountains or other planes.


Spoofing involves mimicking GPS satellite transmissions, which tricks the target receiver into believing it is receiving the correct data as expected. So it is a targeted type of jamming that can direct the plane into enemy territory or collisions on purpose. Jamming can be intentional or unintentional, but spoofing is intentional.

But since spoofing equipment generates multi-satellite signals from the same source, modern-day sophisticated receivers with direction finding can detect and filter out these false signals. But sophisticated spoofing attacks can alter GPS signal parameters to originate from different sources, so you need obfuscation-resilient spoofing algorithms to block the malicious signals.

Is The Military Interfering With GPS Signals?

Yes, but not with the wrong intention. The Air Force and other branches of the United States military are aware of the attacks above. And they rely on GPS more than commercial airlines to navigate and locate their fighter planes, tanks, ships, and troops. So they are more at risk if the systems experience attacks.

An F35 lightning II fighter jet in flight

An F35 lightning II fighter jet in flight

This situation has made them conduct military tests to monitor how US forces can operate without GPS if adversaries employ electronic warfare. Similarly, the military does these tests to monitor the effectiveness of their electronic warfare countermeasures.

Other GNSS systems like China’s BeiDou, Russia’s GLONASS, and Europe’s Galileo are also vulnerable to jamming and spoofing attacks but operate at different frequencies. So there have been cases of ships using GPS receivers being directed to the wrong locations while ships using BeiDou navigate to the right and exact location.

Also, there have been cases of GPS jamming in Northern Europe by Russia, while Galileo remains unaffected.

A Galileo satellite in orbit

A Galileo satellite in orbit

So the United States has enough reasons to modify and test its navigation system to prevent attacks and security threats in the future. Unfortunately, these tests cause GPS outages to commercial users, including airlines, causing near-fatal incidents.

Pilots can fly, land, and navigate manually using visual aids, legacy radio, and other backup technologies. However, the widespread use of GPS and its 99.9% reliability has made most pilots forget manual flying techniques. So the 0.01% unavailability of GPS-based services creates chaos in the cockpit.

Reported Incidents

A passenger aircraft almost crashed into a mountain in Idaho after encountering GPS interference when flying in smoky conditions in August 2018. If it were not for a last-minute intervention by air traffic control, the consequences of the jammed broadcast signals would be fatal.

In another case, a pilot got a “GPS Position Lost” warning when approaching El Paso International Airport in West Texas. After contacting the airline’s operation center, the pilot learned that the White Sands Missile Range was disrupting the signal. So he had to land the plane without vertical guidance on runway 04, which has a high CFIT (Controlled Flight Into Terrain) probability caused by the threat of the climbing terrain in the local area.

Are Military GPS Tests Threatening Airlines? The White Sands Missile Range museum

The White Sands Missile Range museum

Pilots usually log these flight experiences into NASA’s ASRS (Aviation Safety Reporting System), an anonymous posting forum that allows them to share safety tips and near misses.

Air traffic controllers also encounter these issues. For instance, in December 2012, an air traffic controller noticed a passenger plane heading westbound veered 16 km off course. The cause was military GPS jamming, and the controller notified the pilots to change course. However, the ATC also noted that the plane would have collided with an eastbound plane if the pilots had noticed the error earlier and adjusted course.

Are Military GPS Tests Threatening Airlines? An air traffic control team at work

An air traffic control team at work

The Actual Numbers

The ASRS contains a wide range of reports filed by pilots, air traffic controllers, flight crew, maintenance mechanics, and UAS crew, pilots, & visual observers. But the flight disruptions caused by GPS outages might be more common than the logged incidences in ASRS. FAA data showed hundreds of aircraft lost GPS data in 2017 and 2018 when flying near military test areas.

For instance, 21 aircraft experienced and reported GPS disruption issues on a single day in March 2018 to air traffic control near LA. These planes included 12 commercial passenger planes, eight private jets, and a medevac helicopter. Some aircraft flew uninterrupted, while others required ATC assistance, five of which veered off course.

So there are possibly thousands of GPS disruptions in the US annually because the military conducts these tests almost daily somewhere in the country. And each case is a potential accident because most pilots rely on GPS-enabled autopilot systems.

But the cases are more common near remote military bases in the American West.

Are Military GPS Tests Threatening Airlines? A military base

A military base

Does The Military Issue Notices Before Conducting GPS Tests?

Although the military claims to take great care not to affect civilian aircraft, there is enough evidence to show otherwise. So they also issue NOTAM (Notice To Airmen) warnings to inform pilots of upcoming GPS tests.

But these notices can cover thousands of square kilometers. For instance, some inform of interruptions throughout Texas or in the airspace above the US Southwest. These areas are massive, and the NOTAM means the military might disrupt GPS on the entire location. So the interruption might or might not happen. This uncertainty creates problems and can catch some pilots off guard.

NOTAM warnings can also catch air traffic controllers off guard, yet they are the last line of defense for pilots.

Are Military GPS Tests Threatening Airlines? An air traffic controller monitoring several flights

An air traffic controller monitoring several flights

The RTCA looked into this issue and concluded that the NOTAM system was part of the problem because most pilots flying through the affected locations don’t encounter outages. So they ignore the warnings in the future. Therefore, they concluded NOTAM warnings are unrealistic, and the military should narrow down the affected areas to the precise location.

Additionally, several factors can affect GPS interference. They include:

  • Airplane altitude and attitude
  • Terrain
  • Distance from and angle to the interference center
  • Equipment on the plane
  • Flight direction, etc.

So an airplane can experience GPS interruption while another flying nearby might not. These inconsistencies along the different flight profiles make pilots and ATC lose trust in the NOTAM system.

Will Flying Be Safe and Unaffected By GPS In The Future?

The RTCA report made several recommendations to enhance the coordination between the FAA and the Department of Defense. Additionally, it advised the military to avoid doing GPS tests during periods of high air traffic. Other recommendations included the following.

  • The NOTAM system should be easier to interpret and contain warnings closely matching pilot and ATC experiences.
  • Overhaul of the FAA data collection and analysis system
  • Better documentation of adverse events
  • Matching of anecdotal reports with digital data

Wrap Up

In conclusion, military GPS tests are threatening airlines. But these interferences are unintentional because the DoD means no harm to the citizens the government has tasked it to protect. The tests are necessary for national security, so the only solution is to adopt safety recommendations like the ones provided by the RTCA.

That’s it for this article. Drop a comment below if you think we left something out or have ever experienced a GPS blackout when flying. We would like to hear from you. Cheers!

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