St Elmos Fire during Aerial Refueling of E-4 by KC-135

A USAF KC-135 Aircraft is preparing to refuel a USAF E-4. The same aircraft used as Air Force One. The weather that we were going through causes the differential static equalization between the two aircraft. Once the boom touches the receptacle of the E-4 the charges are equalized and the static stops. This is commonly known as St Elmos Fire.