How a woman saved two young children from a life of child sex abuse while on a plane.

Warning: This article contains information about child abuse which may be distressing for some readers.

A woman on a domestic flight is credited with saving two children from sexual abuse when she read the texts of a fellow male passenger mid-flight.

According to The Mercury News, the female passenger, a pre-school teacher from Seattle who wishes to remain anonymous, was on a flight bound for San Jose on Monday when she noticed the man in front of her sending explicit messages.

His messages reportedly referenced him sexually molesting young children, and could be read by other passengers due to enlarged font and a large phone screen.

"It was in large font, and she sees certain words and starts contemplating there's something bigger there," San Jose sex-crimes Detective Nick Jourdenais told The Mercury.

"Then the conversation transitions to children. That's the moment when she decided to preserve the evidence as best as she could."

The woman took pictures of his messages, and alerted flight crew. The man was arrested by police officers working in the airport terminal when the flight landed.

Michael Kellar, 56, reportedly dismissed his messages as "sexual fantasy and role-playing", but FBI agents were able to pin-point the home of 50-year-old woman Gail Burnworth on the receiving end of his texts.

There, authorities confirmed that two children - aged five and seven - were being sexually abused. Investigators believe the man was texting sexual requests to the woman, who was carrying them out on the two children.

Police have declined to discuss the children's relationship to the suspects.

The man is being held without bail on suspicion of two felony counts each of attempted child molestation and solicitation of a sex crime.

The woman is charged with felony counts of sexual exploitation of a minor, rape of a child and dealing in depictions of a minor engaged in sexually explicit conduct.

The female plane passenger is being praised for her quick-thinking and vigilance in protecting vulnerable children.

"We always preach 'If you see something, say something'," Detective Jourdenais said.

"It was apparent to her to say something. She wasn't going to take this home.

"She sees herself as a guardian and protector. It should be acknowledged.

"It's kind of mind-blowing. She gets on a plane, a normal citizen minding her business. A couple of hours later, she’s intervening on quite possibly the most traumatic thing children can go through.

"This was life-altering for them."

If you or someone you know is in need of help, please call the National Sexual Assault, Domestic and Family Violence Counselling Service on 1800 RESPECT.