Southwest Airlines reports that an expectant mother traveling on Flight 441 from Chicago to Salt Lake City delivered her baby onboard. NBC News reports that a medical service on the radio helped a doctor on the plane deliver the baby.

"It was very exciting!" a flight attendant said.

"We looked around for strings," said Dr. John Saran, who helped deliver the baby. "So I pulled my shoe strings out of my shoes, so that baby is walking around with my shoe strings around its umbilical cord."

Saran was on his way to Salt Lake City from Chicago. He has an internal medical practice in Chicago.

"When I first saw the head coming out, I said, 'Great! At least it's not the back end!'" he joked.

The flights attendants onboard the plane weren't completely trained to deliver a baby.

"They do receive some training. There are some brief procedures in their manuals, but they treat all of these things whether it's a heart attack or the delivery of a baby as a medical emergency," 9NEWS Aviation Expert Greg Feith said.

Brandon Morse was a passenger on the flight. He spoke with 9NEWS shortly after its landing.

"They announced on the PA and asked if anyone had any blankets," Morse said. "About 15 minutes later they got on the PA and announced we had a new passenger, a baby boy."

Morse says the whole plane clapped when the announcement was made.

"One of the flight attendants walked through the cabin and said, 'We have a new boy. We have a new boy just to let everyone know what is going on.' Everyone was just stunned," he said.

Another passenger, Katherine Williams, said everyone was surprised to learn a baby had been born on the plane.

"At first we just heard clapping in the back. That's when I first thought, 'Is someone having a baby?' Because they never let us know. And so I thought, 'There is clapping happening!'" Williams said.

The flight made the unexpected landing at Denver International Airport Friday morning and was met at the gate by an ambulance.

"They immediately turned the plane around mid-flight and we landed here in Denver. They got them out, the dad, mom and baby and took them off to the hospital," Morse said. "All the Southwest staff did an excellent job, really calm. Everything was great. Everything seemed really healthy."

The Medical Center of Aurora said the mother and baby are doing well.

"They [the passengers] were making jokes about calling it Southwest or Westin - something like that," Williams joked.

Some passengers on board said the mother planned on giving her baby up for adoption.

The family asked for privacy on Friday.

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