On September 22nd, during an Iranian celebration of the start of the 1980-88 Iran-Iraq war, two of the military aircraft flying over the event collided, and both crashed. The two pilots in the F-5 fighter ejected and survived, but the other aircraft, Iran's sole AWACS (radar command and control) aircraft, went down with all seven of the crew on board.
The AWACS was actually the last of two Iraqi AWACS that fled to Iran during the 1990-1 war with the coalition assembled in the area to liberate Kuwait from Iraqi occupation. Iraq "sold" the two AWACS to Iran for a nominal sum. The Iraqis originally had three AWACS, but one was destroyed during a 1991 coalition air raid. The three AWACS were based on the Russian Il-76 transport. The first one had a radar installed in the cargo hold, but the others, with French assistance, had a more powerful radar installed. The Iranians have managed to keep one of these AWACS flying, and it radar operating, by smuggling in spare parts and hiring mercenary technical experts as needed.
The AWACS crashed near the tomb of former Iranian religious leader, and founder of the religious dictatorship currently ruling Iran, Ayatollah Ruhollah Khomeni. Iran has suffered a growing number of military and civilian aircraft losses over the last decade. This is partly because the various embargos on Iran make buying new aircraft difficult, and smuggling in spare parts not much less difficult. There is also a lot of corruption and mismanagement in the organizations that maintain military and commercial aircraft. Letting the F-5 (a 1970s U.S. light fighter) get so close to the slower moving Il-76 AWACS was obviously not a competent move.