What Really Happened in the American Airlines Flight 191 Crash

On the morning of May 25, 1979, a McDonnell Douglas DC‑10 bound for Los Angeles never left the runway at Chicago’s O’Hare International Airport. Within seconds of lifting off, the aircraft rolled left, plunged nose‑first, and shattered on a nearby highway. The tragedy, known as the American Airlines Flight 191 crash, claimed every passenger and crew member aboard—258 passengers and 13 crew—as well as two people on the ground, making it the deadliest aviation accident on U.S. soil at that time.

The Day the DC‑10 Fell

Flight 191 was a routine Chicago‑to‑Los Angeles run. The crew completed a standard pre‑flight checklist, and the aircraft taxied to runway 32R under clear skies. As the thrust levers advanced for takeoff, the left‑hand engine (the #1 engine) lurched violently and detached from the wing. Simultaneously, the left wing’s leading‑edge slat retracted, causing a sudden loss of lift on that side. The plane yawed sharply, rolled, and struck the runway before cartwheeling into the adjacent North Western Avenue, igniting a massive fireball.

Why the Engine Came Loose

Investigators traced the engine’s separation to a maintenance error that dated back weeks earlier. During a routine engine change, a shop crew removed the #1 engine but failed to reinstall the three critical retaining bolts that secure the engine pylon to the wing. Instead, a makeshift “cutter” was used to pry the engine out, and the bolts were left out of the aircraft entirely. When the engine was later re‑attached, the bolts were never replaced, creating a hidden weakness that manifested under the stress of takeoff.

The missing bolts meant the pylon’s attachment points could not bear the aerodynamic forces generated by the engine. As the aircraft accelerated, the pylon fractured, the engine tore away, and the hydraulic lines that ran through the pylon were severed. This loss of hydraulic pressure disabled the left wing’s slats and the primary flight‑control surfaces, leaving the pilots with an aircraft that was both under‑powered on one side and aerodynamically compromised.

The NTSB Investigation

The National Transportation Safety Board (NTSB) launched a massive probe, combing through wreckage, maintenance logs, and interviewing the airline’s mechanics. Their report concluded that the primary cause was the improper maintenance practice, specifically the failure to reinstall the engine‑retaining bolts. The board also noted that the aircraft’s design contributed to the disaster: the hydraulic lines and control systems were routed through the pylon, making them vulnerable when the engine separated.

In addition to the mechanical failure, the NTSB highlighted shortcomings in the airline’s quality‑control procedures. The maintenance shop had been operating under a “fast‑track” schedule, and there was inadequate supervision to verify that critical steps—like torque‑checking the bolts—were completed. The report’s findings spurred sweeping reforms across the industry.

Aftermath and Industry Changes

In the wake of the crash, the Federal Aviation Administration (FAA) issued new directives that reshaped how airlines handle engine removals. Key changes included:

• Mandatory torque verification: Technicians must now record and confirm the torque values for all critical bolts before an aircraft can be released for flight.
• Redundant hydraulic routing: New aircraft designs separate essential hydraulic lines from engine pylons, reducing the risk of total system loss if an engine detaches.
• Enhanced oversight: The FAA increased on‑site inspections of airline maintenance facilities, emphasizing compliance with procedural checklists.

The DC‑10 itself faced intense scrutiny. While the aircraft’s overall design was not deemed inherently unsafe, the incident prompted Boeing to redesign the pylon‑hydraulic integration on subsequent models. Airlines also revised crew‑training programs to better prepare pilots for sudden asymmetrical thrust loss and control‑surface failures.

Remembering the Victims

Every year, families and aviation enthusiasts gather on the anniversary to honor those lost. Memorials at O’Hare and along the crash site’s highway serve as somber reminders of the human cost behind technical failures. The tragedy also reinforced the public’s demand for transparency and rigorous safety standards—principles that continue to guide modern aviation safety culture.

Frequently Asked Questions

What caused the American Airlines Flight 191 crash?

The immediate cause was the loss of the left engine due to missing retaining bolts after an improperly performed engine change. This led to hydraulic failure and loss of critical flight controls.

How many people died in the crash?

All 258 passengers and 13 crew members aboard perished, along with two individuals on the ground, for a total of 273 fatalities.

What safety reforms resulted from the investigation?

The FAA mandated strict torque‑verification procedures for critical bolts, redesign of hydraulic routing to avoid single‑point failures, and increased oversight of airline maintenance operations.

Did the DC‑10 design contribute to the accident?

While the DC‑10’s overall design was not declared unsafe, the routing of hydraulic lines through the engine pylon was identified as a vulnerability, prompting redesigns in later aircraft.