Mass. EMA and State Police report troopers, local police and the National Guard will be doing training exercises this week in locations that will include Boston Harbor and Gillette Stadium.

The excercise even has a code name - Vigilant Guard - so, as Mass EMA says:

Residents can anticipate seeing an increased presence of military and civilian emergency first responders, military vehicles, use of sirens, and regular flights of military helicopters throughout the Commonwealth.

Last year:

Military copters buzz downtown, scare people half to death.

The year before:

The super-secret helicopters are back, endlessly circling Boston Harbor and making kids think we're having an earthquake.

Blatant commercial shilling:

Universal Hub Copter Recon Unit T-shirt.