空中和地面的目击者称，他们惊恐地看着喷气发动机的部件爆炸并破裂从丹佛起飞后不久，碎片散落在房屋上。

尽管在科罗拉多州布鲁姆菲尔德周六的事件中没有伤亡报告，但居民和乘客告诉美国广播公司新闻，他们仍然感到震惊。

“这更像是‘嘿，一切都会好起来吗？’“这不正常，”布雷特·盖伊告诉美国广播公司新闻，他是联合航空328号航班的乘客我不知道该怎么想。"

美国联邦航空管理局表示，这架波音777-200的右引擎在周六下午1点左右从丹佛飞往檀香山的航班起飞后不久出现故障。当发动机被火焰吞噬时，部分零件开始脱落，碎片掉落在半空中。

国家运输安全委员会周日晚上表示，根据他们的初步调查，进气口和整流罩与发动机分离，两个风扇叶片断裂。

根据NTSB的说法，一个叶片的一部分被嵌入到密封环中，一些风扇叶片的叶尖和前缘出现损坏。

盖伊说，他和其他乘客听到了吊杆的声音，看到发动机从他们的窗户上分开。

“飞机摇晃得很厉害，”他回忆道。“这并没有停止，也没有人真正知道。然后，你向窗外看去。”

布鲁姆菲尔德的居民泰勒·塔尔告诉美国广播公司新闻，那天下午发动机爆炸时，他正和家人一起散步。塔尔说，他和他的家人在听到爆炸和看到闪光后感到害怕。

他越来越关心乘客，因为他看到飞机在发动机着火的情况下继续飞行。

“这跟我们见过的任何东西都不一样。所以我担心我的女儿，我的妻子，我只是担心，知道飞机上挤满了人，”塔尔说。

塔尔说，他希望飞机能在剩余发动机的情况下安全着陆。

盖伊在飞机上的座位上也有类似的想法，他想起了1986年汤姆·克鲁斯的电影《壮志凌云》中的一个瞬间。

“有一部分是这样的，一号引擎坏了。然后他说，‘我要关掉它，’”他回忆道。“出于某种原因，在我的脑海里，我在想，‘我们可以用一个引擎，但这有点乱。’"

据美国联邦航空局(FAA)称，飞机返回丹佛国际机场，所有231名乘客和10名机组人员在没有任何重大受伤的情况下离开。

然而，引擎碎片对下面的房屋和街道造成了巨大的破坏。飞机的巨大部分，包括金属覆盖物，落在屋顶、人行道和树上。

科比·克莱恩斯告诉美国广播公司新闻，当他们听到爆炸声时，他和妻子正在家里。他们跑到他们的前窗，看到一个巨大的圆形发动机从他们身边滚过。

“发动机罩最终就在这里，挂在我的树枝上，”他说。“它掉了下来，正好落在我车库角落里我卡车的床上。它掉了下来，落在地上，就在那里结束了，我和我妻子坐在里面，问，“那是什么？”"

克莱恩斯说损坏非常可怕。

“如果有人在那里受了重伤或死亡，”他说。“我是说...卡车的整个顶部都在驾驶室的侧面。”

克莱恩斯说，他和妻子从新闻中听说飞机安全着陆，截至今天下午，残骸仍在他的财产上。

“所以，非常幸运的是，地面上没有人因附近发生的几起大爆炸而受伤，”他说。"谢天谢地，飞机上没有人受伤，也没有任何人受伤."

当联邦航空局和NTSB调查损坏和调查事故时，残骸散落在整个城镇。

美国联邦航空局局长史蒂夫·迪克森周日发布了一项紧急适航指令，要求立即或加强对配备普惠公司PW4000发动机的波音777飞机的检查。

迪克森在一份声明中说:“这可能意味着一些飞机将停止使用。”。

在美国联邦航空局发布指令后不久，联合航空公司宣布将从其时间表中暂时删除24架由这些发动机驱动的波音777飞机。

该航空公司在一份声明中表示:“自昨天以来，我们一直与NTSB和美国联邦航空局的监管机构保持联系，并将继续与他们密切合作，以确定需要采取哪些额外措施来确保这些飞机符合我们严格的安全标准，并能够恢复服务。”。"当我们调换飞机时，我们预计只会给一小部分顾客带来不便。"

一位知情人士告诉美国广播公司新闻，这种特殊的发动机具有独特的设计。刀片本身是中空的钛，来源将其比作巧克力复活节兔子。

美国广播公司新闻顾问、前NTSB航空安全办公室主任汤姆·霍特称发动机风扇叶片对调查“至关重要”。

他告诉美国广播公司新闻，“NTSB想看的是，有没有任何证据表明，发动机和风扇叶片已经存在问题。”。

United Airlines passengers, pedestrians recall horror of watching engine rain debris

Eyewitnesses in the air and on the ground said they watched in horror and shock as parts of a jet engine exploded and broke apart shortly after takeoff from Denver, raining debris over homes.

Although there were no reported injuries or deaths during Saturday's incident over Broomfield, Colorado, residents and passengers told ABC News they are still shaken up.

"It was more along the lines of, 'Hey, is everything going to be OK?' That's not normal," Brett Guy, who was a passenger aboard United Flight 328, told ABC News. "I didn't know what to think."

The Boeing 777-200's right engine failed shortly after takeoff around 1 p.m. Saturday for a flight from Denver to Honolulu, the Federal Aviation Administration said. Parts of the engine began to strip off as it was engulfed in flames, and debris dropped in midair.

The National Transportation Safety Board said Sunday evening that based on their initial investigation, the inlet and cowling separated from the engine and two fan blades were fractured.

A portion of one blade was embedded in the containment ring, and some of the fan blades exhibited damage to the tips and leading edges, according to the NTSB.

Guy said he and other passengers heard the noise of the boom and saw the engine come apart from their windows.

"The plane was shaking pretty hard," he recalled. "It didn't stop, and nobody really knew. And then, you looked out the window to the side."

Tyler Thal, a resident of Broomfield, told ABC News he was walking with his family that afternoon when the engine exploded. Thal said he and his family were scared after hearing the explosion and seeing the flash of light.

He grew more concerned about the passengers as he saw the jet continue to fly with the engine on fire.

"It's nothing like anything we've ever seen. So it was fear for my daughter, my wife, and I [was] just concerned, knowing that that plane is full of people," Thal said.

Thal said he was hoping that the plane could make it safely with the remaining engine.

Guy also had a similar thought while he was in his seat on the plane after he remembered a moment from the 1986 Tom Cruise movie "Top Gun."

"There's the part where it's like, engine one is out. And then he's like, 'I'm shutting it down,'" he remembered. "And for some reason, in my head, I was thinking, 'We're OK with one engine, but this is kind of messed up.'"

The plane returned to Denver International Airport, and all 231 passengers and 10 crew exited without any major injuries, according to the FAA.

The engine debris, however, caused massive damage to homes and streets below. Huge parts of the plane, including the metal coverings, fell on roofs, sidewalks and trees.

Kirby Klements told ABC News he was in his home with his wife when they heard the boom from the explosion. They raced to their front window and saw a giant, circular piece of the engine roll right past them.

"The engine cowling ended up laying right here hanging off of my tree branch," he said. "It had come down and landed square in the bed of my truck at the corner of my garage. It fell over and landed and ended right there with my wife and I sitting right inside here going, 'What is that?'"

Klements said the damage was very scary.

"If somebody would have been in there that had been seriously injured or killed," he said. "I mean ... the whole top of the truck is in the side of the cabin of the truck."

Klements said he and his wife heard about the plane making a safe landing from the news and that as of this afternoon, the debris was still on his property.

"So that was very fortunate that nobody on the ground got hurt from the several large pieces that hit around the neighborhood," he said. "And thank goodness that nobody in the plane was injured or anything either."

Debris remains scattered throughout the town as the FAA and NTSB survey the damage and investigate the incident.

FAA Administrator Steve Dickson issued an emergency airworthiness directive Sunday that would require immediate or stepped-up inspections of Boeing 777 airplanes equipped with certain Pratt & Whitney PW4000 engines.

"This will likely mean that some airplanes will be removed from service," Dickson said in a statement.

Shortly after the FAA issued its directive, United announced it would temporarily remove 24 Boeing 777 aircrafts powered by those engines from its schedule.

"Since yesterday, we’ve been in touch with regulators at the NTSB and FAA and will continue to work closely with them to determine any additional steps that are needed to ensure these aircraft meet our rigorous safety standards and can return to service," the airline said in a statement. "As we swap out aircraft, we expect only a small number of customers to be inconvenienced."

A person familiar with the situation told ABC News this particular engine has a unique design. The blade itself is hollow titanium and the source compared it to a chocolate Easter bunny.

Tom Haueter, ABC News Consultant, and former NTSB Director of the Office of Aviation Safety, called the engine fan blades "critical" to the investigation.

"What the NTSB wants to look at is, is there any evidence of a preexisting issue with that engine, with that fan blade," he told ABC News.

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