The American Civil Liberties Union is raising questions about the appearance of government surveillance planes in the skies over Baltimore amid protests over Freddie Gray’s death in police custody. On Thursday, Friday and Saturday night, a Cessna plane registered to “NG Research” flew loops around West Baltimore, where protesters burned cars and a CVS earlier in the week. Another plane with no tail number flew wider loops around the area on Saturday night. An anonymous government official told The Washington Post the flights were aerial support Baltimore police officials requested from the FBI. The planes reportedly use infrared technology to monitor people’s movements.