Unidentified Plane Causes Roar in Skies A plane breaking the sound barrier is believed responsible for a loud explosion in the sky that startled residents of the Abington-Rockland-South Weymouth area Sunday afternoon. Residents who rushed from their homes on hearing the bomb- like roar reported seeing a speedy delta-winged aircraft overhead about 2 P.M. A check with the South Weymouth Naval Air Station revealed that no craft based there is capable of breaking the sound barrier and that no transient aircraft landed at the base Sunday.