There were four total, but only two were sent at first with the other two as bac...

sp332 on May 5, 2011 | parent | context | favorite | on: Mysterious US Helicopter Used in Bin Laden Raid

There were four total, but only two were sent at first with the other two as backup. When one of those went down, one of the backup helicopters was sent in.

astrodust on May 5, 2011 [–]

This is the importance of backups.