A Perth woman who held a stranger's two-month-old baby as she died in her arms aboard an international flight has described the incident as "the most confronting situation one could possibly go through".

Key points: Nadia Parenzee offered to help the baby's parents after she became distressed

Nadia Parenzee offered to help the baby's parents after she became distressed The baby, who she called Farah, died in her arms as she tried to soothe her

The baby, who she called Farah, died in her arms as she tried to soothe her She said the parents from Saudi Arabia were starting a new life in Australia

Nadia Parenzee was a passenger on AirAsia flight D7236 from Kuala Lumpur to Perth early this morning when she offered to help a couple whose baby was "really restless" and crying continuously.

"I could see by looking at them that they were a little bit distressed, the baby was crying a lot, but then I could see the stewardess was giving a bottle to the baby, so I thought 'OK, maybe it's just hungry'," she said.

About 10 minutes later Ms Parenzee, a mother and former nurse, was sitting in her chair half asleep when there was "a vigorous tap" on her shoulder from one of the cabin crew.

"I could see this look on the parents' [faces]. They just sort of handed the baby to me," she said.

"I took the baby straight away and I could see that she was grey in colour and she was struggling to breathe, so I said a little prayer.

"As soon as I said that, she went limp and I just said to the stewardess, 'this is a medical emergency, this is not a baby in distress'."

Nadia Parenzee said she tried to sooth the baby girl, but then she stopped breathing. ( ABC News: Frances Bell )

Ms Parenzee said she was about to start resuscitation, but urged the crew to make a medical call to the cabin.

"I was screaming, 'we need a doctor, we need a doctor,' and about 20 people came running," she said.

Ms Parenzee said doctors started CPR immediately, while others searched the plane's medical box for equipment.

"It was chaos, absolute chaos, because I think by this point, the parents had realised there was something dramatically wrong with the baby," she said.

"I had known when I looked at the baby's pupils and they did the light test that the baby had passed."

After 15 minutes, Ms Parenzee said she went and spoke to the pilot about making an emergency landing.

"The pilot said, 'you know, we can go to Jakarta, obviously it's going to take time to get clearance. We're two and a half hours away from Perth.

"I said, 'well, go to Perth if we're going to get medical assistance straight away."

Doctors continued trying to resuscitate the baby girl for two hours, including as the plane landed in Perth, where she was received by medical staff waiting on the tarmac.

Parents were 'starting a new life' in Australia

Ms Parenzee said the baby's father told her his family was moving to Australia "to start a new life".

"[He said] 'we've heard so many good things about Australia. I'm doing my PhD here. I just want a better life for us'," she said.

A ground staff member at Perth International Airport carries a pram off the plane. ( ABC News: Frances Bell )

The baby girl was the Saudi couple's first child, Ms Parenzee said, adding that the pair had taken her to see a doctor a week ago to treat a cold.

"The parents were just genuinely beside themselves," she said.

"I was trying to reassure them.

"The plane was very sombre. No one moved. Everyone was very quiet and patient."

Ms Parenzee was full of praise for AirAsia staff, who she said dealt with the situation "really well".

"It's not an easy thing to go through," she said.

"It's very surreal. She was so tiny."

An AirAsia spokesman confirmed there was a "medical emergency" on board the flight, which was met by a team of medical specialists and WA Police on its arrival at Perth International Airport.

Officers were investigating the incident and would prepare a report for the coroner.

"We are unable to comment further on the infant's medical situation, however our thoughts are with the infant and family involved," an AirAsia spokesman said in a statement.

Flight delays as investigation carried out

Officials could be seen leaving the plane this morning carrying large brown paper evidence bags.

Police carry bags of evidence off the AirAsia flight as it sits on the tarmac at Perth Airport. ( ABC News: Frances Bell )

An airport staff member was also seen carrying a pram off the aircraft.

The same plane was set to depart at 6:50am as AirAsia flight D7237 from Perth back to Kuala Lumpur, but was delayed by several hours as a result of the emergency.

The AirAsia spokesperson apologised for any inconvenience caused by the delay and said the airline would help travellers to re-book.