Northwest Orient Airlines Flight 710, was a scheduled service from Minneapolis (MSP) to Chicago (MDW) and Miami (MIA). The Lockheed L-188C Electra departed Minneapolis at 12:51 and arrived at Chicago-Midway Airport at 13:55. During the short time the aircraft was on the ground at Chicago, approximately 30 minutes, it was refueled and prepared for continuation of the flight to Miami. The flight took off from Midway Airport at 14:38. At 15:13, Flight 710 reported over Scotland, Indiana, maintaining 18000 feet and estimating Bowling Green, Kentucky, at 15:35. This was the last radio contact with the flight. At 15:25 the outboard engines and engine support structures, the complete right wing, and the outer portions of the left wing and ailerons separated in flight. The aircraft crashed out of control. PROBABLE CAUSE: “The Board determines that the probable cause of this accident was the separation of the right wing in flight due to flutter induced by oscillations of the outboard nacelles. Contributing factors were a reduced stiffness of the structure and the entry of the aircraft into an area of severe clear air turbulence. “