One footage that appeared to be taken from inside the plane showed an engine on fire. Another video on social media showed a cloud of black smoke being left by a plane. Something blew up, a man on the video can be heard saying. In an audio recording, a pilot is heard saying Mayday, aircraft just experienced engine failure, need to turn immediately, according to audio from the monitoring website liveatc.net which was reviewed by Reuters. Flight 328 from Denver to Honolulu experienced an engine failure shortly after departure, returned safely to Denver and was met by emergency crews as a precaution. There are no reported injuries on board and we will share more information as it becomes available, United Airlines spokesperson David Gonzalez said in a statement.