The Boeing Model Two Ninety-Nine, the Gust Lock Nobody Removed, and the Preflight Checklist Born from the Crash That Almost Ended the B-17 Before It Began

The modern preflight checklist traces its origin to a single mechanical oversight on October 30, 1935, at Wright Field, Dayton, Ohio. When the Boeing Model 299 - the prototype that would become the B-17 Flying Fortress - crashed on its Army Air Corps evaluation flight, the cause was not a design flaw or an engine failure. The gust locks had never been removed. Two experienced professionals died. And the people who investigated the wreck changed how aviation manages human fallibility forever.

What Was the Boeing Model 299?

Boeing’s Model 299 was unlike any military aircraft the Army Air Corps had evaluated before. Powered by four Wright R-1820 Cyclone radial engines producing 750 horsepower each, it weighed more than 21,000 pounds empty and could carry up to 8,000 pounds of bombs. Its top speed of 252 mph at altitude exceeded most Army pursuit aircraft of the era.

The competing entries from Martin and Douglas were capable two-engine designs. The Model 299 was something else entirely - a heavily armed flying warship, bristling with gun positions at the nose, belly, and multiple fuselage stations. Seattle newspapers had already dubbed it the “Flying Fortress” after its maiden flight out of Boeing Field in July 1935.

Boeing had made an enormous corporate gamble. The company spent hundreds of thousands of dollars of its own money on the prototype, without a contract in hand, during the depths of the Great Depression. Winning the Army evaluation meant securing the company’s future.

The Crew and the Flight

Major Ployer Peter Hill, age 43, the Army Air Corps project officer, took the left seat. Leslie Tower, age 41, Boeing’s chief test pilot who had flown the airplane’s first flight three months earlier, sat in the right as the manufacturer’s representative. Both were seasoned, careful professionals.

The Model 299 was the most complex aircraft most military pilots had ever encountered. It demanded management of four throttle levers, four mixture controls, four propeller pitch controls, a retractable landing gear system, wing flaps, turbocharger controls, multiple fuel tanks with transfer valves - and a full gust lock system that clamped the control surfaces when the airplane was parked.

Gust locks prevent control surfaces from banging against their travel stops in ground winds. Installing them on parking is standard procedure. Removing them before flight is equally standard. On the morning of October 30, that removal did not happen.

The Crash and Its Cause

The Model 299 taxied to the runway, ran up to full power, and lifted off exactly where the performance numbers predicted. Then the nose climbed steeply - far beyond any normal departure attitude. With the elevator gust locks still engaged, pitch control was effectively fixed. The airplane stalled, rolled left, and came down hard.

Major Hill died within hours at the base hospital. Leslie Tower died two days later from burns. Two other crew members were injured. The airplane was destroyed.

The investigation was methodical and unambiguous. No structural failure. No engine malfunction. No design defect. A required preflight step - one that experienced pilots had performed hundreds of times on other aircraft - had simply not been performed. On an airplane of this complexity, there had been no written, itemized procedure requiring anyone to verify it.

Why the Contract Went to Douglas - and Why It Didn’t End There

The Army’s evaluation rules were clear: a competitor that crashed was disqualified. The contract went to the Douglas B-18, a competent twin-engine design that met the original specification. Boeing had no recourse.

But the Air Corps officers who had watched the Model 299 fly before the crash knew what they had seen. They arranged the separate purchase of 13 service test aircraft, designated YB-17, funded outside the original competition. They were not prepared to let the most capable bomber they had evaluated disappear because of a preflight oversight.

Those evaluation pilots then addressed the underlying problem directly.

The Birth of the Preflight Checklist

The Model 299 was too complex to manage by memory alone. The solution those Army Air Corps pilots developed was neither complicated nor obvious for the era: a written, structured, itemized procedure that the crew runs through, in sequence, verifying each critical item, every single time, without exception.

Before start. Engine start. Before takeoff. After takeoff. Cruise. Descent. Before landing. After landing. After engine shutdown.

By most accounts in aviation safety history, this was the first formal, structured preflight checklist designed specifically to manage the operational complexity of a modern multi-engine aircraft across a complete flight sequence. It acknowledged a simple truth: the best pilots are not the ones who rely on memory. They are the ones who check.

The concept did not stay with the B-17. The airlines adopted it. The military embedded checklist procedures into every subsequent aircraft type. As general aviation aircraft grew more capable, the practice followed. Every student pilot who opens a Cessna 172 Pilot’s Operating Handbook and runs the before-start checklist is following a direct line back to Wright Field in October 1935.

The B-17’s War Record

The YB-17 service tests validated the design. The Air Corps began ordering the type in quantity, and by the time the United States entered World War II, the B-17 had become the cornerstone of the Army Air Forces’ strategic bombing campaign in Europe.

Over 12,000 were eventually built, rolling out of Boeing’s Seattle plant and from Douglas and Lockheed-Vega production lines, heading to England and the Eighth Air Force and the sustained air campaign over Germany.

The men who flew them were young - twenty, twenty-two years old, former farm workers and students and factory hands who found themselves at high altitude in a narrow aluminum fuselage, waist gun positions open to minus-40-degree Fahrenheit slipstream over German targets. The Eighth Air Force absorbed bomber losses that are difficult to comprehend in retrospect. And before every mission, those crews ran the checklist - because what had happened to the Model 299 had become embedded in the culture of the aircraft before many of those men were old enough to shave.

What the Wreck Left Behind

Fewer than a dozen B-17s remain airworthy today. When one taxis past at an airshow, the sound of four large radials at high power is something felt in the chest as much as heard. The weight of that moment goes beyond machinery. It is the surviving member of a line of aircraft built in the thousands, flown by the tens of thousands, in a war that demanded everything they had.

It also represents the reason every checklist in every aircraft cockpit exists in the form it does.

The gust lock that was not removed on October 30, 1935, killed two experienced, competent pilots. The investigation that followed asked not just who failed, but how to design a process so that human memory is never the single point of failure. That is not bureaucracy. That is engineering applied to human fallibility.

Every item. Every time.

Key Takeaways

• The Boeing Model 299 prototype crashed on October 30, 1935 at Wright Field, Ohio, killing Major Ployer Peter Hill and Leslie Tower after the gust locks were not removed before flight.
• The airplane was the most capable bomber the Army Air Corps had ever evaluated, outpacing contemporary pursuit aircraft at 252 mph with four engines and armed gun positions at every angle.
• The crash disqualified Boeing from the contract, but Air Corps officers arranged a separate purchase of 13 YB-17 service test aircraft to preserve the design.
• Investigation of the crash led directly to the development of the first formal structured preflight checklist in aviation history, designed to remove human memory as a single point of failure.
• That checklist concept spread to commercial aviation, military aviation, and general aviation - and underpins every POH checklist used by pilots today.