with M2AC machine-guns and LAU-68A 70-mm rocket launchers. Three additional units were ordered in 1996 and delivered as attrition replacements in March 1998. Black Hawks wore 1191 to 1194 serials and are being used for special operations. Although the FAM received 18 surplus Bell 206s from the Attorney General's office (PGR) in the mid-1990s, the main need identified by the FAM High Command was for a new fleet of transport helicopters that would allow it to support the Army with an adequate airlift capability. Recent times On September 16, 1995, after more than 30 yearly military parade flights without incidents, an F-5E collided in mid-air with three Lockheed T-33s during the parade for the Independence of Mexico. All aircraft were lost and a total of 10 deaths occurred. Since then, for safety reasons, military parade flyovers in Mexico have been smaller in participation. In 2004, the Mexican Air Force recorded a UFO sighting over southern Campeche. In 2007, after more than 45 years in service, the last operational T-33s were retired. In 2012, the F-5 fighter jets had their 30th anniversary in Mexican Air Force service. Due to high operating costs, lack of parts, and the extreme age of the aircraft, the Mexican Air Force retired all but 3 F-5s in late 2017. In early 2019, the Mexican Air Force received repaired engines for their F-5 fighters, as part of an effort to return a handful of the aircraft to operational status. Because of the ongoing Mexican Drug War, increasing importance has been placed on acquiring airborne surveillance platforms, UAVs, light attack aircraft, helicopters and rapid troop transports. On 21 February 2021, a Learjet 45XR operated by the Mexican Air Force crashed while taking off from El Lencero Airport in Veracruz, killing all six people on board. Structure A national commander under the orders of the Secretary of National Defense is in charge of the Mexican Air Force. The second-in-command is the Air Force Chief of Staff, who supervises a Deputy Chief of Operations and a Deputy Chief of Management. The Air Force divides the country's territory into four regions: Northwestern (Mexicali, Baja California), Northeastern (Chihuahua, Chihuahua), Central (Mexico City) and Southeastern (Tuxtla Gutiérrez, Chiapas); each region is commanded by a general. The regional headquarters are in charge of 18 air bases across the country: Ranks Air Force ranks are the same as in Mexico's Army, with the exception of