What Caused United Airlines Flight 173 To Go Down, And How Did It Subsequently Change The Aviation Industry?

A photo showing a large section of the fuselage among the wreckage of United Airlines Flight 173.

It was December 28, 1978, and United Airlines Flight 173 circled through the winter night sky above Portland, Oregon. Thousands of feet below, rows of houses and empty streets slept silently, unaware that a passenger jet was drifting closer to disaster with every tick of the clock. Inside the cabin, things were just as calm: seatbelts fastened, suitcases stored safely away, and passengers relaxed into their seats as the plane prepared for landing. No one could see the danger coming. But with every loop over the City of Roses, the plane was inching closer to its tragic fate. 

Moments later, the plane went down and tore into a residential neighborhood, killing ten of the 189 people on board. At first, nobody could wrap their head around how everything had gone so terribly wrong. After all, the aircraft, a McDonnell Douglas DC-8, was fully functional, the weather was calm, and the pilots had decades of experience under their belt. This accident became one of the most infamous case studies in aviation history, demonstrating how human errors can be just as dangerous as mechanical ones.

To fully understand the underlying causes of this catastrophe, we must first take a look at the moments leading up to the crash. Flight 173 was scheduled to depart Denver for Portland, a routine domestic route. However, as the aircraft began its approach into Portland International Airport, the crew noticed a vibration and noise they had never heard before. Concerned that the landing gear might not be fully extended or properly locked, the captain decided to keep the aircraft hovering in a circular pattern to buy more time for investigating the issue further. Instead of landing immediately, he instructed the flight engineer to check the landing gear indicators and troubleshoot any problems. 

However, it was not the mechanical malfunction that sent the plane down, but the decisions made by those flying it. As the aircraft continued circling the airport, its fuel supply dwindled with each passing minute. The flight engineer repeatedly warned the captain that fuel levels were running dangerously low, but his hesitant, indirect warnings were not enough to command the captain’s attention. Making matters worse, air traffic control was not clearly informed of the fuel emergency until it was too late. Before long, all four engines flamed out, and the plane crashed just short of the runway.

After thoroughly investigating, it was determined that the landing gear issue was not the cause of the crash: the gear was fully functional and capable of supporting a safe landing. The real problem was captain fixation, an aviation phenomenon in which a pilot becomes so laser focused on one problem that they overlook other, more pressing issues. In this case, the captain fixated on the landing gear problem, leading him to forget about fuel management. It’s important to acknowledge that the captain isn’t the only one at fault. After all, the flight engineer had immediately recognized the looming threat but did not communicate his concerns forcefully enough to make them seem anything more than suggestions. All in all, this accident exposed the dangers of cockpit hierarchy, a strict chain of command that airlines historically operated under. For decades, captains were rarely questioned, even when their decisions put the aircraft and everyone in it at risk.

A map showing the route Flight 173 had taken on the day of the accident, with departure at New York City (JFK), a stopover in Denver (DEN), and arrival at Portland (PDX).

Like other significant aviation tragedies, United Airlines Flight 173 has inspired many impactful safety reforms. The most important outcome of this accident was the improvement of Crew Resource Management (CRM). CRM training teaches pilots that safety is a collective responsibility. All crew members, regardless of rank or position, are expected to speak up when they identify a safety concern.

Secondly, after the crash, airlines revised fuel monitoring procedures. Aviation officials now enforce the consistent tracking of fuel levels, and when they reach a hazardous threshold, pilots are required to inform air traffic control immediately and prioritize landing above all other concerns. The accident also highlighted that there is no room for vague or polite language in the cockpit. Aviation training now stresses the importance of using direct statements in times of crisis.

Lastly, before Flight 173, accidents were often attributed to the failure of a single pilot or engineer. However, this crash prompted aviation towards a systems-based approach. Airlines began redesigning training programs to address human psychology, stress, and decision-making, among many other technical factors.

In contrast to many other flights, where problems emanate from a single defect or hardware malfunction, United Airlines Flight 173 is still studied because it illustrates how even the most experienced professionals can make catastrophic mistakes under pressure. As we can see, there was no sudden emergency that forced the plane down. The crash was a slow one, taking nearly an hour to culminate in such a tragic end. 

Nowadays, aviation standards emphasize teamwork, assertive communication, and fuel awareness. The lives lost near Portland redefined how pilots work together and how risks are managed in the cockpit. Because of the lessons learned, countless future accidents were able to be prevented.