The FAA has announced that Defense Department tests will disrupt GPS signals from time to time between January 20 and February 22 in the southeastern US. Pilots will be warned about the tests, which are expected to make GPS signals either unreliable or unavailable for up to 45 minutes at a time. There is apparently no plan to warn the general public, and there is no indication of the degree to which land-based GPS signals will be disrupted. There is essentially no information about what is tested, how it can affect GPS signals, or whether or not there are any environmental or public health issues involved.