The night of April 17th, New Yorkers were rattled by the sound and sight of low flying helicopters buzzing around southern Manhattan. In this case, there was nothing to be alarmed about; New York City had announced that the flights would occur and the gents flying the helicopters are the best in the world: The Nightstalkers.
160th Special Operations Aviation Regiment (SOAR), commonly known as the Night Stalkers, are the helicopter pilots who fly Special Operations missions around the globe. They bring a highly unique set of capabilities to the table not found in any other military. The unit was created after the fiasco at Desert One in 1980 after which it was realized that Special Operations units, to include Rangers, SEALs, and Delta Force, required their own dedicated aviation assets.
160th routinely conducts joint training exercises within the United States with the units that they will be deploying with overseas. Sometimes these exercises take the form of pre-mission training for an upcoming deployment. Others are readiness exercises, and once in a while, they are dress rehearsals for specific classified operations such as the raid that killed Osama Bin Laden — the rehearsals took place at the CIA’s Harvey Point facility. On other occasions, these flybys are conducted as a show of force just prior to major events like G12 summits or the Olympics to warn any terrorists plotting an attack that they will be facing the varsity team if they do anything stupid.
The Night Stalkers and their JSOC counter-parts such as Delta Force have previously conducted such exercises in Manhattan, seemingly every few years. Normally the way these exercises work is that the there is a full mission profile set up in which the island of Manhattan is notionally designated an enemy nation for the sake of the training mission. JSOC operators will than clandestinely infiltrate into Manhattan, collect intelligence on the training targets, and then the assaulters can begin their own mission rehearsals. Finally, 160th spins up their helicopters and the assault force is flown into Manhattan to rescue a hostage, capture/kill a High Value Target (HVT), or whatever other tasks they have been assigned.