One-Eleven N1553 departed New Orleans, LA at 18:35 for a passenger flight to Minneapolis, MO with intermediate stops at Shreveport, LA, Fort Smith, AR, Tulsa, OK, Kansas City, MO and Omaha, NE. Flight 250 departed Kansas City at 22:55 on an IFR clearance to Omaha at FL200. However, the crew asked if they could remain at 5000 feet because of the weather. The flight remained at 6000 feet until permission was received at 23:06 to descend to 5000 feet. At 23:08 the crew contacted a company flight which had just departed Omaha. This flight reported moderate to light turbulence. About four minutes later the aircraft entered an area of an active squall line. The One-Eleven violently accelerated upward and in a left roll. At this time the right tailplane and the fin failed. The aircraft then pitched nose down and within one or two seconds the right wing failed as well. The plane tumbled down in flames until stabilizing into a flat spinning-attitude before impacting the ground. Braniff regulations prohibit a plane from being dispatched into an area with a solid line of thunderstorms; however the company forecast was somewhat inaccurate with respect to the number and intensity of thunderstorms and the intensity of the associated turbulence. PROBABLE CAUSE: “In-flight structural failure caused by extreme turbulence during operation of the aircraft in an area of avoidable hazardous weather.”