Owen, who looked out his window around 4:30 to see what the racket was, was among many people reporting three military Osprey helicopters Read more.

Matthew George watched one of the National Nuclear Security Administration's helicopters fly low over the Marathon route today for our annual background-radiation check.

Erik P. Kraft reports the copter hovering over Harvard Square today was hired by the university to take infrared images of 46 of its buildings. Why would they do that? To find roof leaks, he says.

UPDATE: Helicopters are buzzing the area around Egleston Square as well.

Once again, reports are flooding into Helicopter Central here of low-flying, buzzing, really loud choppers just making loops around Boston Harbor, from Logan to Aquarium and back again, over and over again, so we're going to assume they're part of the same mysterious Pentagon/police training exercises we're not supposed to know about, except it's kind of hard to ignore giant blacked out eggbeaters roaring over your heads. Read more.

Neil photographed one of the helicopters that ferried Congressional Medal of Honor recipients around town to various ceremonies today - in this case, parked outside the World Trade Center, where the recipients were holding their national convention.

Mad Ty photographed an airborne Blackhawk helicopter: Read more.

Roving UHub photographer Jim Gavaghan got what may be the day's best photo of the Department of Energy's National Nuclear Security Administration radiation-background helicopter, which was flying low and loud over and near Boston Harbor today. He saw it past the trees along L Street in City Point.