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Some Alaska GPS users may notice problems this month. Here’s why.

Eielson Air Force Base is conducting GPS signal-jamming exercises through next week that may disrupt navigation systems throughout Interior Alaska, particularly for pilots.

Air Force Lt. Kayshel Trudell, a spokesman for the larger training exercise that includes the GPS signal jamming, said the tests will happen only on weekdays between 4 p.m. and 7 p.m. to minimize disruption to the public. The jamming will last until May 24, according to a base statement.

“Civilian pilots will be some of the most affected, possibly encountering GPS signal loss during the jamming window,” Trudell said in an email.

The impact to aircraft will vary depending on the pilot’s altitude and distance from the facility conducting the tests, which is centered southwest of Eielson near Delta Junction. A pilot flying at 10,000 feet may lose signal if they’re within 437 nautical miles of Eielson, and a pilot flying at 4,000 feet might have problems if they’re 371 nautical miles away, according to the statement.

Ted Stevens Anchorage International Airport is about 209 nautical miles from the jamming center, putting its pilots within the affected radius. If any safety issues arise, though, the base has a contingency plan to shut off power to its jamming equipment, Trudell said.

“The goal of this training is not to inconvenience people, but to ensure our military forces are ready to operate were they to face a loss of GPS in a real world situation,” Trudell said.

People on the ground are less likely to see an impact, he said. Drivers using in-vehicle navigation or smartphone navigation apps, for example, might lose signal intermittently depending on how close they are to Eielson.

The exercise is designed to train pilots, who rely on GPS-based navigation systems, to contend with situations where an adversary might try to cripple them by jamming the signal. Trudell said the training is part of a larger exercise called Northern Edge 2019, a joint-force training meant to prepare U.S. troops to respond to crises in the western Pacific and Indian Ocean regions.