Experts say the plane and engine used by United have a safe track record - and the scary landing in Colorado should have minimal impact on the airline

• A United Airlines jet made an emergency landing after an engine failure on Saturday.
• Three aviation regulators have effectively grounded Boeing 777s with PW4000-112 engines pending an investigation.
• Experts say the issue isn't likely systemic with the plane or engine, given the track record of both.
• Only 69 aircraft in the world are affected, and United is the only US carrier with the model.

Regulators in the US, UK, and Japan have moved to effectively ground Boeing 777 aircraft powered by the Pratt & Whitney PW4000-112 engine pending an investigation into the United Airlines flight that made an emergency landing shortly after takeoff over the weekend.

Flight 328 from Denver, Colorado to Honolulu safely returned to the airport after an uncontained engine failure occurred shortly after takeoff. The incident resulted in debris falling to the ground in Denver suburbs, but caused no death or injury to passengers or bystanders as the engine failure did not affect other critical aspects of the aircraft.

The grounding affects 69 aircraft currently flying for carriers including United, All Nippon Airways, and Japan Airlines, and is supported by Boeing, the aircraft's manufacturer. Impact to United, the only US carrier affecting by the grounding, should be minimal, experts told Insider.

"We're very lucky that the fan blades didn't shatter the cabin, they didn't puncture the wing, they didn't puncture a fuel tank," Henry Harteveldt, founder of travel research company Atmosphere Research Group, said in an interview. "As accidents go, this was as good as you can hope in that there was no injury, no death, and the airplane returned safely to the ground."

The incident mirrored a similar issue with the same airline, aircraft, and engine, per Aviation Safety Network data, as a 2018 United flight from San Francisco to Honolulu similarly experienced an engine issue and was able to land safely with no injuries or loss of life. But experts don't believe that there's a systemic problem with the engine or the aircraft itself, noting the track record of safety for both.

"This was the launch engine for the plane back a quarter-century ago," Richard Aboulafia, vice president of analysis at Teal Group, told Insider, as the Boeing 777 has been in commercial service since 1995. If there was an inherent problem with this specific combination of engine and airframe, Aboulafia says we would've known about it already.

The first fatal Boeing 737 Max crash, for example, occurred just over one year into its commercial life. The Boeing 777, on the other hand, has over 25 years of service under its belt with no hint of such troubles. The full investigation will reveal whether the incident was an unforeseen problem with the engine or the aircraft, or whether it was a mechanical issue on United's end.

What experts don't agree on, however, is why that particular engine and airframe combination was grounded by regulators around the world. Harteveldt told Insider that the grounding and inspection requirements set by the Federal Aviation Administration and others may be due to the heightened safety environment that exists in aviation following the 737 Max grounding of March 2019.

"I think the FAA wants to err very much on the side of caution in the wake of what happened with the 737 Max to understand what this problem is," Harteveldt said.

The FAA was criticized in the wake of the 737 Max crashes for a lack of oversight and was one of the last regulators to ground the now-notorious aircraft. Now, the agency is taking an "extremely cautious" approach to this incident, according to Harteveldt.

"This is definitely an extraordinary step that's being taken, but it's being taken out of intelligent prudence," Harteveldt said. "What United, the FAA, and Pratt & Whitney want to do is understand what caused these fan blades to come apart."

Aboulafia called the move "par for the course" as there are so few Boeing 777 aircraft with this type of engine currently flying.

"This is what you would do given this incident," Aboulafia said.

What happens to United

It remains to be seen how long the grounding will last and how long it will take the airline to perform the required inspections, which will determine the overall impact..

In the interim, flights that were scheduled to be flown by the Pratt & Whitney-powered Boeing 777s in the next few days will be swapped for other aircraft like the Boeing 787 Dreamliner or Boeing 777-300ER, depending on factors like passenger demand, and distance for a particular route.

"The grounding of these 24 planes to United will definitely affect the airline's operation," Harteveldt said. "But if there is a time for something like this to happen, it is now, when United is operating far fewer flights than it normally does because of COVID."

This type of aircraft typically spends its life flying overseas routes, but the pandemic has grounded most of those flights. That takes some of pressure off United since the aircraft aren't needed as much as they would be if air travel were at 2019 levels.

"I don't think it's going to be more than an operational headache," Aboulafia said.

United's analysts are likely troubleshooting the mid to long-term effects of the grounding, according to Harteveldt, and how it will affect operations as the airline heads into the spring and summer season.

Cargo is also an important factor that will determine United's next move as airlines have been relying on freight revenues to make up for the loss of passengers. The loss of 24 Boeing 777-200s, as one of the airline's largest aircraft, will reduce United's cargo-carrying ability in the short-term.

The Chicago-based airline, however, still has a fleet of active Boeing 777-200 aircraft currently flying passengers and cargo, the difference is that they're equipped with General Electric engines and not the PW4000-112 used on Saturday's aircraft. Airlines typically choose one engine to fly a particular fleet but United acquired the General Electric-powered aircraft as a result of a merger with Continental Airlines.

United also may consider pulling planes out of storage if the grounding lasts more than a few weeks. The airline has aircraft currently sitting in storage that could be brought back up to the majors; though, it might take around one to two weeks per plane to get them back into flying condition.

Regardless of the path United takes, Aboulafia says the grounding should have "zero impact whatsoever" on the airline's overall recovery from the COVID-19 pandemic.