Transcript for Passengers speak out after engine cover detaches mid-flight
We'll stick to the skies but a little different. Midair scare to show you. Everybody, take a look at your screens. I'm no aviation expert but pretty sure that's not supposed to happen. Part of an engine cover detached midflight and forced to make an emergency landing and David Kerley has the story. What in the world is going on there? Reporter: T.J., quite a scene, isn't it? The jet tens of thousands of feet in the air when part of that engine detaches but as you can see it, it was still flapping and the passengers saw it all. A frightening sight right out passengers' windows, a piece of the engine flapping in midflight. Part of the engine's cover which broke loose shortly after this united airline flight took off Sunday morning. The pilots of the Orlando bound jet quickly calling controllers. We need to get back to Denver relatively quickly. When you get a chance, nature of the emergency. The panel has become dispatched from the airplane. We have about 6 hours of fuel and 196 people. Reporter: It was a half hour after takeoff the jet turned around landing safely back at Denver before 8:30 in the morning. Take a look at that mangled panel with the interior of the engine exposed. Passengers who were not sitting near the wing getting a chance to see the engine on the ground. This pilot really took some pretty heroic, decisive action and made a big decision turning us around really quickly. That pilot potentially saved lives. Reporter: United saying it lantdzed at the airport due to a mechanical issue. The flight landed safely and taxied to a gate where customers deplanned normally. Experts agree it is a disconcerting sight but that is only there for aerodynamic reasons, doesn't affect the operation of the engine. Still a little bit scary for they all got on another aircraft and got to Orlando, T.J. That makes me feel better, David, don't mind this piece just flapping in the wind there. We got more disconcerting aviation news talking about Boeing 737 maxes, have been grounded for safety reasons. Another issue about an earlier version of that 737. Reporter: Yeah, it's called the next generation, the Ng, 737 Ng and what Boeing has found is that the attachments of the wing to the fuselage in some of them are cracking much earlier than they ever expected. These are fatigue cracks, so they've asked and the FAA has ordered that all airlines check this to see if they're having any cracks where the wingwings attach to the fuselage. Planes and cracks. All right. David, thank you so much.
This transcript has been automatically generated and may not be 100% accurate.