In racing, a black flag is a warning to a driver that they are doing something improper or driving in an unsafe manner. If a driver sees a furled black flag, they should consider it a warning and either proceed to the start to speak with an official or stop their offending activity immediately. A black flag during racing means that the driver most likely illegally gained position(s) somehow, and they must drop back at least three racers. In FIA International-permitted series, the black flag means an immediate disqualification for the driver involved. The car number of the summoned driver is displayed on the finish line. In some cases, the black flag is waved at all observation posts simultaneously to order all drivers to clear the track after the starter waves the red flag, often in the case of a serious accident.