A United Airlines flight en route from Denver to Honolulu suffered a catastrophic engine failure over the Denver area on Saturday, sending debris raining onto homes and a park in Broomfield.
The incident is drawing international attention, especially as dramatic photos and video of the aircraft’s flaming engine and the debris that fell onto the ground are shared wide and far. But there’s important context to the images.
Here are four big things you should know about the flight and the plane, a Boeing 777-200, involved in the incident:
MORE: United Airlines plane with exploded engine drops debris over Denver area before emergency landing
The flight lasted only about 25 minutes
Flight 328 was only in the air for about four or five minutes when it started turning back toward Denver International Airport. That’s the point at which one of the two pilots flying the plane called air traffic controllers to report the engine failure.
The plane reached a maximum altitude of 13,500 feet, according to FlightAware, a website that tracks flights. The plane reached a maximum speed of 382 miles per hour.
The plane had just passed Rocky Mountain Metropolitan Airport when it began its return to Denver.
A Boeing 777-200 like the one that was involved in Saturday’s engine failure can reach an altitude — or has a service ceiling — of more than 43,000 feet. It can fly between 5,200 and 7,000 nautical miles depending on whether it is an extended range version.
The plane was well below its cruising altitude, according to FlightAware, when it turned back to the airport.
The Boeing 777-200
There are a few things you should know about the Boeing 777-200, which is among the world’s safest and most technologically advanced aircraft, that will help you understand what happened Saturday.
Like most two-engine airplanes, it is designed to safely fly on only one engine in an emergency situation. Pilots train for this kind of situation frequently.
U.S. and international air regulators used to require planes to have more than two engines for long flights like the one United Flight 328 was on Saturday. But as aircraft engines have become more reliable, and since planes can fly with only one engine with relative ease, those requirements have been relaxed.
The Boeing 777-200 is the second largest airplane in United’s fleet. Only the Boeing 777-300ER is larger.
The 777 is a workhorse for United. It flies on high-demand domestic routes and many international routes. It is economical and has a very long range.
This kind of engine failure has happened before
There have been a number of well-publicized incidents involving similar uncontained, catastrophic engine failures on other aircraft types.
In 2010, a Qantas Airbus A380 suffered an uncontained engine failure shortly after takeoff from Singapore. Shrapnel from the engine damaged critical systems on the plane, but pilots were able to land safely. The incident was blamed on faulty manufacturing of a pipe in the Rolls Royce engine.
Catastrophic engine failures are most dangerous when they damage critical flight systems on a plane, like an aircraft’s hydraulics. Those systems are what enable pilots to fly the plane.
In 1989, United Airlines Flight 232 en route from Denver to Chicago suffered a catastrophic engine failure. The DC-10’s flight control systems were severely damaged and 112 people died when the plane made an emergency landing in Iowa.
In Flight 328’s case on Saturday, the plane was able to quickly return to Denver International Airport. It’s possible that the people on the ground who escaped falling debris faced more of a risk than those in the air.
(No one was injured aboard the plane or on the ground, though there was some property damage in the Broomfield area.)
We probably won’t know what happened very soon
The National Transportation Safety Board is already sending investigators to Denver to help probe what happened on Saturday. But the investigation process is not a short one.
It will be months, if not years, before the agency releases a final report on what caused the engine failure.
It took nearly three years for the NTSB to release its final report on the fatal crash of a business jet in Aspen in January 2014.
The Associated Press contributed to this report.