A search and rescue effort is under way for a downed US F-15 fighter jet in southern Iran. It is not known how many crew members were on board.

Images posted on social media and verified by CBS News showed a refueling plane and two helicopters flying low over Khuzestan Province, consistent with a search and rescue mission. Iran's state media claimed Iranian forces shot down the plane. The governor of Iran's southern Kohgiluyeh and Boyer-Ahmad province says that the priority is “capturing" any downed US crew "alive”. “Those who succeed in capturing or killing hostile enemy forces will be specially commended by the Governor’s office", he adds, according to a report by semi-official ISNA news agency. Meanwhile, Iranian outlets have said that a reward of 10 billion tomans (around £50,000) has been set by traders of the province for anyone who finds the American “intruder”.

Debris of a downed aircraft that originally was posted to social media show wreckage consistent with that of an F-15E Strike Eagle. These are dual-role fighter jets designed for both air-to-ground and air-to-air missions. In Iran, they are most likely to have been involved in Defensive Counter Air roles to shoot down Iranian drones and cruise missiles. In its air-to-ground strike role, the jet is a weapons platform capable of dropping laser and GPS guided precision munitions, as well as other bombs.

The aircraft has two crew: the pilot in the front who flies the jet and a Weapons Systems Officer in the back seat. The "Wizzo" has four screens in front of them and is responsible for selecting targets and making sure the weapons are properly programmed for the appropriate attack profile. This two-crew system allows the workload to be divided up, particularly in a congested air environment where the pilot is trying to evade threats.

Short range, infra-red guided MANPADs are portable systems that remain a serious threat in Iran because they can be quickly moved around. The use of flares "popped" by targeted aircraft is the most common means of trying to defeat Surface-to-Air Missiles (SAM). US military commanders have often talked of air superiority over parts of Iran in this war, but this incident, if confirmed to be a shoot-down, shows how the dangers very much remain. (BBC)