NOTICE TO WEST COAST UAV OPERATORS: Starting June 7, it appears the US military will be testing a device or devices that will potentially jam GPS signals for six hours each day.

The FAA issued an advisory warning pilots on Saturday that global positioning systems (GPS) could be unreliable during six different days this month, primarily in the Southwestern United States.

On June 7, 9, 21, 23, 28, and 30th the GPS interference testing will be taking place between 9:30am and 3:30pm Pacific time. But if you’re on the ground, you probably won’t notice interference.

The testing will be centered on China Lake, California—home to the Navy’s 1.1 million acre Naval Air Weapons Center in the Mojave Desert. The potentially lost signals will stretch hundreds of miles in each direction and will affect various types of GPS, reaching the furthest at higher altitudes. But the jamming will only affect aircraft above 50 feet.

Read the official FAA Advisory.