If you've seen or heard low flying helicopters in the greater Boston area, police want you to know it's all part of a training drill.
They've tweeted out a "community advisory," about the training, and say the the Department of Defense, along with local and federal law enforcement, are doing the training through Friday.
It's called a "planned exercise" in cooperation with local authorities, and "not in response to any current world events."
Boston Police say the exercise is expected to have minimal impact to the public.
They hope to release more information when the training is complete.