Early reports indicate that the pilot of a US F-15 fighter aircraft downed over Iran was rescued - which, if confirmed, would be the latest in the long history of US combat search-and-rescue missions over decades. The search operation is ongoing deep inside Iran for a second crew member, according to CBS, the BBC's US partner.

Combat search and rescue (CSAR) missions are considered among the most complex, time-sensitive operations that US and allied militaries prepare for. In the US, elite units of the air force are specially trained for CSAR missions and are often pre-emptively deployed near conflict areas where aircraft could be lost.

Put simply, CSAR missions are military operations aimed at finding, aiding, and potentially rescuing personnel in need, including downed pilots and isolated troops.

The missions are extremely time-sensitive, as enemy forces would likely be deployed in the same area to try and locate the same US personnel the CSAR teams are trying to rescue. Iranian officials have urged citizens to find the missing US crew member alive and are offering rewards for their capture.

According to a former commander of a pararescue jumpers squadron, a rescue operation like the reported one in Iran would involve at least 24 pararescue jumpers scouring the area in Black Hawk helicopters. Verified video that emerged from Iran appeared to show US military helicopters and at least one refuelling aircraft operating over Iran's Khuzestan province.

This intense rescue scenario emphasizes the harrowing nature of CSAR missions, where military personnel operate amid potential enemy threats to save their comrades.