A New Jersey millionaire was sentenced to seven years in prison on Monday evening after pleading guilty to an ongoing sexual relationship with a 15-year-old girl, including one incident on his private plane after he set it on autopilot, according to federal prosecutors.

Stephen Bradley Mell, a 53-year-old former CEO of a New Jersey investment firm, pleaded guilty in December to one count of interstate travel to engage in illicit sexual conduct and one count of receipt of child pornography, according to U.S. Attorney’s Office in New Jersey. On Monday evening, he was also sentenced to five years of supervised release, fined $40,000, and ordered to pay restitution of $35,200 and an assessment of $5,000.

Prosecutors allege Mell, a licensed pilot and father of three, already had “a pre-existing relationship with the minor” when he began communicating with the 15-year-old through Snapchat in July 2017, according to the federal complaint.

“In fact, it was the minor’s mother who first introduced Mr. Mell to obtain flight lessons for the minor,” court documents state.

The conversations quickly turned sexual, prosecutors allege, when Mell asked the teenager “if she knew how to perform oral sex.” A few days later, Mell invited the 15-year-old to “spend time alone” at his Bedminster home about an hour outside of New York City.

In one message, Mell allegedly wrote: “Trust me the sex is amazing but so is being around you.”

On three occasions throughout the summer, Mell “performed oral sex acts” on the girl, according to the complaint. During a July 20, 2017 meeting, Mell flew with girl in his private plane from Somerset Airport to Cape Cod “for the purpose of engaging in illicit conduct, specifically, a sexual act with a person under the age of eighteen."

On the flight back, Mell put the “aircraft in autopilot mode and engaged in sex acts,” the complaint states.

“Miss you so much,” Mell allegedly Snapchatted the teenager at one point.

Prosecutors say Mell also asked 15-year-old to send him texts, SnapChat photos, and FaceTime video chats of the teenager engaging in “sexually explicit conduct.” During one sexual encounter in New York City, Mell took a photo where the teenager’s “genital area clearly visible” with his cellphone, the complaint alleges.

Mell’s legal team argued on Monday evening the father of three was a “human man” who fell into “a spiral of depression.” The 53-year-old was allegedly struggling with survivor’s guilt after giving up his seat on a 2012 fatal helicopter trip with friends.

Robert Bianchi, his attorney, did not immediately respond to The Daily Beast’s request for comment.

Mell, the former president and chief executive an investing firm that specialized in municipal bond markets, also faces another prison sentence after pleading guilty in May to third-degree endangering the welfare of a child by engaging in sexual relations with a female victim under the age of 16.

Prosecutors said the 53-year-old will be sentenced on July 12.