TACOMA – A federal grand jury has indicted a Washington state couple accused of sexually abusing children after an airline passenger reported seeing text messages about the abuse on a man’s phone during a flight.

The U.S. Attorney’s Office says 56-year-old Michael Kellar and 50-year-old Gail Lynn Burnworth were indicted Wednesday and will be arraigned later this month.

They were charged with conspiracy to produce child pornography, the News Tribune reported.

Kellar was also charged with attempting to entice a minor and Burnworth was also charged with child rape, molestation and sexual exploitation of a minor.

Lawyers for the two declined comment.

They were arrested after a passenger reported seeing text messages on Kellar’s phone discussing giving children drugs so they would be unconscious while being abused.

The plane passenger told authorities that Kellar was sitting in front of her and texting about the abuse with a large font on a large smartphone. The font and screen were so big that the passenger was able to take photos of Kellar’s text conversation, police said.

The passenger alerted the flight crew.

A federal pornography charge conviction would mean a minimum of 15 years in prison, and could result in a sentence up to twice that. The enticement charge could result in a 10-year minimum sentence and up to life behind bars.

Police in San Jose, California, arrested Kellar in the city’s airport July 31 after a flight from Seattle.