It might be 2021, but Boeing is having a flashback to 2019. Two years after Boeing’s 737 Max planes were grounded due to safety issues that led to two fatal crashes, some of its 777s are now under scrutiny for engine malfunctions.

On Saturday, a United Airlines flight from Denver to Honolulu had to make an emergency landing when the aircraft’s right engine failed 20 minutes after takeoff. It appears that two engine fan blades fractured, setting the engine on fire and creating an explosion that blew off parts of the engine. Those parts fell to the ground, scattering large pieces of debris near houses and in public parks. The entire front casing of the engine landed in front of a house in Broomfield, Colorado. No one in the aircraft or on the ground was hurt.

Boeing is now urging all airlines to ground 777 planes containing Pratt & Whitney PW4000 engines. According to NBC News, those engines are only used in Japan, Korea, and the United States. United Airlines has grounded all of its 24 777 planes currently in service. In Japan, Japan Airlines and All Nippon Airways have grounded all 32 of their 777 planes containing the specific engine. The Guardian reports that there are 69 777 planes containing Pratt & Whitney PW4000 engines currently in service around the world.

Three years ago, a 777 operated by United Airlines went through a similar incident when the cowling of the right-hand engine was blown off 45 minutes before landing. A right engine malfunction also caused a Japan Airlines 777 flight to return to the Naha airport in December.

Two hundred forty-one people were on the flight from Denver to Honolulu, many of whom were understandably afraid. Travis Loock, a passenger on the flight, told CNN, “There was a big boom and the kind of sound you don’t want to hear when you’re on the airplane. And I instantly put my shade up, and I was pretty frightened to see that the engine on my side was missing.”

Full inspections of all Boeing 777s with the same engine (120 of them, with only 69 in service) will be carried out before the aircraft are clear to fly again.