Navigation systems including those found in commercial flights may be disrupted or jammed completely across the southwest U.S. over the next couple of weeks. That sounds pretty bad but do not be too alarmed, it’s not Red Dawn. It’s just the U.S. Air Force and its based out of Nellis Air Force Base in Nevada, as reported by .

The Red Flag exercises started on Jan. 26 and are scheduled to continue until Feb. 16, meaning commercial flights that often utilize GPS systems in various flight procedures, including taking off and landing (no big deal), may encounter outages over the next couple of weeks.

The National Business Aviation Association (NBAA) warned that the training exercises would be conducted between 8 p.m. PST and 11 p.m. PST and could impact most of the southwest, according to :

The NBAA Command Center reports the U.S. military will begin training exercises on the Nevada Test and Training Range between 0400Z until 0700Z daily. Training maneuvers will impact vast portions of the Western U.S. including California, Nevada, Oregon, Wyoming, Arizona, Utah, Colorado, Montana and New Mexico. FAA enroute ATC centers affected include Albuquerque (ZAB), Denver (ZDV), Los Angeles (ZLA), Salt Lake (ZLC), Oakland (ZOA) and Seattle (ZSE). Operations in R-2508 and R-2501 may also be impacted.

Flights in the Los Angeles area have been warned to expect issues with navigation systems at any altitude, which means they will not be able to rely on certain navigation-based take-off and landing equipment and procedures. Las Vegas will see most of the direct impact from the exercises, with some flights potentially being re-routed away from LAS due to increased flight traffic in the area.

The greater region could experience potential takeoff and landing delays of 30 minutes or more during peak exercise hours, and particularly on Thursday, Friday and Saturday nights.

The Red Flag exercises are meant to test the effectiveness of military strike operations in a simulation that is as realistic as possible. This could suggest that the GPS jamming is an additional challenging element for the forces involved in the exercise, which include the U.S. Air Force, U.S. Marine Corps, U.S. Army, U.S. Navy, UK’s Royal Air Force and Royal Australian Air Force.

An Australian EA-18G Growler involved in the exercise erupted into flames during takeoff from Nellis Air Force Base on Saturday and five people were treated for injuries, the reported.

GPS jamming is a relatively new nuisance for both the military and civilian population. Jamming works by disrupting the relatively weak GPS signals and blocking signal connection with receivers on everything from a phone to a battleship. According a 2012 , the South Korean military reported systems disruptions from a North Korean signal in 2010. Latvia and Norway experienced GPS outages that were suspected of being inadvertent disruptions resulting from Russia’s military exercises in August and September of last year, as reported by .

Illegal GPS jammers the size of a cigarette lighters can be purchased online, which can jam phones, GPS systems and tracking devices within a radius of 16 feet or more. In 2015, a Federal Communications Commission (FCC) investigation revealed that a jamming device in a vehicle parked near Northeast Philadelphia Airport was affecting plane systems up to a mile out from the airport, according to . The owner of the vehicle claimed he was using the jammer to block a tracking device. Newark airport experienced a similar issue in 2009, according to NovAtel.

Very little public information is available about military applications of GPS jammers. In 2016, the Air Force released information concerning a GPS jamming exercise at China Lake in California. Here are the details of that test and a released image, according to :

The FAA has issued a Notice to Airmen (NOTAM) [PDF] that on June 7, GPS readouts will be unreliable or nonexistent for 253 nautical miles (291 miles) at 50 feet above sea level, for 340NM (391 miles) at 4,000 feet, and for 375NM (431 miles) at 10,000 feet, covering a huge area of very busy airspace. The above map shows the Los Angles Basin, the San Francisco Bay Area and Las Vegas in Nevada are among the areas affected in some way.

In addition, the FAA is warning pilots flying the Embraer Phenom 300, one of the world’s most popular executive jet aircraft, that the testing could interfere with flight stability controls and has said extra care should be taken in the area.

That article also pointed out that the UK’s Office of Communications had scheduled to conduct similar jamming tests throughout July of 2016. It’s clear that the militaries of the world view GPS jamming as a serious threat, and the Air Force’s operations exercises may be preparing for it. The military could also be testing systems or devices that block jamming to maintain a signal connection.

If you have any travel plans that have you in the sky over the southwest in the later evening over the next couple of weeks, just be prepared for delays and hope your pilots haven’t forgotten how to fly without the soothing voice feeding them turn-by-turn directions, or however plane navigation works.

Southwest Airlines informed Jalopnik in an email that it was aware of the training and, so far, had not seen any impact. Jalopnik reached out to the U.S. Air Force public affairs office and other major airlines operating in the area for comment, and will update when more information is available.

This article has been updated with an additional link to The War Zone’s reporting connecting the expected disruptions and outages to the Red Flag military exercises.