The helicopter was apparently shot down on Friday while on a reconnaissance mission in eastern Jonglei state.

BBC: Russia demands action over UN helicopter downed in S Sudan

Once Scambos called the British Antarctic Survey, the group sent an aircraft on a reconnaissance mission to examine the extent of the breakout.

CNN: Massive ice shelf on verge of breakup

Twenty minutes before, Mellinger, who goes by Brad but is named Kevin, was running a reconnaissance mission on the banks of the Tigris River when he went down.

NPR: 'Miracle Workers' Save Lives at Balad Field Hospital

The deadliest incident for the DEA occurred August 27, 1994, when a plane carrying five special agents crashed in the Peruvian Andes during a reconnaissance mission, according to the DEA's Web site.

CNN: STORY HIGHLIGHTS

Nato said at the weekend that an unarmed reconnaissance aircraft had been flying a mission over western Afghanistan late last week when its operators lost control of it.

BBC: Iran shows film of captured US drone

Months after the back-to-back, mission-ending dives, the Lunar Reconnaissance Orbiter flew over the crash sites and imaged the final resting spots.

NPR: NASA Moon Craft Spots Ebb And Flow Crash Sites