Just eight years after a severe thunderstorm contributed to the crash of Southern Airways Flight 242, a Delta Airlines flight traveling from Ft. Lauderdale, Fla., to Dallas, Texas, was seconds away from landing when Mother Nature unleashed an invisible killer.

Triple-Digit Heat and a Trigger

Aug. 2, 1985, was another blistering day of triple-digit heat in Dallas although this is quite typical for the heart of summer. Given sufficient moisture and an "atmospheric trigger," the conditions were conducive for thunderstorm development.

Delta Airlines Flight 191 departed Fort Lauderdale in the mid-afternoon. In the cockpit were Captain Edward Connors, First Officer Rudolph Price and Second Officer Nick Nassick. The experienced flight crew was flying a Lockheed L-1011 TriStar aircraft, a reliable workhorse in the Delta fleet.

By late afternoon, the flight was nearing Dallas. At the same time, a weak frontal system began to provide the needed trigger for thunderstorm development. Just before 6 p.m., a shower developed near the airport but was not a cause for concern. In the air, Captain Connors diverted his plane around a thunderstorm in Louisiana.

On Final Approach

As the L-1011 neared the airport, the previously innocuous shower began to intensify. Just 1,500 feet above the ground, on final approach just 1 minute from landing, Captain Connors noted lightning in the cloud ahead of them. Despite the impending storm, the weather report from the airport was not ominous and well within the restrictions for landing.

Just seconds later, at 800 feet above the ground as the plane entered the heavy thunderstorm, a series of rapid events conspired to doom the jet. First the plane accelerated, hit from behind by strong winds. Then, just as suddenly, the plane rapidly lost speed and altitude. The pilots responded by pushing the throttles to maximum power but it was too late.

Without any altitude left, the plane smacked into the ground, ran across a highway killing a motorist, plowed into two water towers and burst into flames, just thousands of feet from the runway. Including the motorist, 137 people died; 29 survived.

Microburst Revealed

How could an aircraft only 800 feet from the ground and seconds from landing crash so violently with no warning?

After a lengthy investigation, the NTSB concluded that windshear and a microburst encountered in the thunderstorm caused the pilots to lose control of their plane.

In 1985, although the effects of wind shear were known by pilots, microbursts had been studied less and pilots had only limited training. In addition, real-time wind shear information was not readily available to pilots.

As thunderstorms gather strength, they produce turbulent winds. These violent gusts are unpredictable and can bring down an airplane in the right circumstances.

In the case of Delta 191, the pilots were not aware of the severity of the windshear and potential downburst that was directly in their flight-path.

In the aftermath of this tragedy, NASA developed sophisticated airborne windshear detection systems that pilots could use while in-flight.

As with the crash of Southern Airways 242, the NTSB recommended improved communication between meteorologists on the ground and pilots in the air. Pilot training was also improved.

In addition, airports at high risk to microbursts were fitted with improved radar technology that allowed meteorologists to detect microbursts in a more timely fashion.

Despite all of the improvements made since 1985, landing in violent weather still presents a safety risk. This was never more apparent than in 1999 when a crew of an American Airlines flight attempted to race Mother Nature and failed.

Stay tuned for the third and final installment of this series, Racing the Storm: The 1999 Crash of American 1420.

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