NBC 5 viewers contacted us via email and Facebook to ask about a "loud boom" in Hood and Johnson Counties Monday morning.
One Facebook post asked if there was an earthquake around the Crowley area.
"It slightly rattled the house, but none of my neighbors can see anything," said one Granbury resident via email.
After a check of the United States Geological Survey (USGS) website showed no sign of an earthquake we made a few phone calls we got this response from Norman Robbins at Lockheed Martin:
The latest news from around North Texas.
Lockheed Martin Aeronautics was contacted this morning by various media outlets reporting that listeners heard a supersonic boom this morning in Johnson County (Godley) and also from the Granbury area. The company did have supersonic flight activity underway this morning and while the activity generally occurs at very high altitudes, atmospheric conditions sometime result in disturbances on the ground. The testing is a normal part of the manufacturing process used for preparing military aircraft for our customers.
Lockheed would not provide any specifics on the type of aircraft being tested.