The U.S. Justice Department is gathering data from cell phones by using communications towers installed on small airplanes, the Wall Street Journal reported on Thursday. The program began operations in 2007 and uses Cessna planes flying from at least five major airports and covering most of the U.S. population, the newspaper said.

The planes have devices that mimic the cell phone towers on board and trick mobile phones into revealing their unique registration data, the report added. They can collect information from tens of thousands of cell phones in a single flight, which occur on a regular basis, the Journal said.

The Department of Justice have not provided any comment yet.