A former CEO of a New Jersey investment firm was sentenced Monday to seven years in federal prison for engaging in sexual activity with a teen girl in his private airplane after he set it on autopilot and receiving nude images of the girl.

Stephen Bradley Mell, 53, of Far Hills, previously pleaded guilty 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 Craig Carpenito.

Mell, who goes by his middle name Bradley, had been president and chief executive of W.H. Mell Associates, a Summit-based investing firm that specialized in municipal bond markets. The company’s website is no longer online and a corporate phone number is no longer in service. Mell had been president of the company since 1995, according to an online profile on the firm’s former website.

Mell traveled from July to December 2017 “for the purpose of engaging in the production of child pornography and sexual acts with a minor (and) admitted knowingly receiving child pornography,” authorities said.

Mell was arrested in June 2018 after authorities discovered he was engaging in a sexual relationship with the girl in Readington and Bedminster townships, authorities said. Mell communicated with the 15-year-old girl starting in May 2017 through text messages and Snapchat and eventually asked her if she knew how to perform a sex act, according to the complaint. He invited her to his Far Hills home the next month, according to federal court records.

The two engaged in sexual conduct on June 20 and July 5, 2017, when Mell was 51 years old and the victim under 16 years old, court documents stated.

On July 20, 2017, Mell flew the girl in his private plane from Somerset Airport to Cape Cod, Massachusetts, “for the purpose of engaging in illicit conduct, specifically, a sexual act with a (minor),” according to the complaint.

On the flight back, Mell put the aircraft in autopilot and engaged in sex acts with the minor. He also received sexually explicit photos of the girl, according to the complaint.

In addition to the prison term, the judge sentenced Mell to five years of supervised release, fined him $40,000 and ordered him to pay restitution of $35,200 and a Justice for Victims of Trafficking Act assessment of $5,000.

Mel also pleaded guilty to a state child endangerment charge in Hunterdon County. He is scheduled to be sentenced on state charge in Hunterdon County on July 12 and the plea agreement calls for a three-years prison term. He will have to register as a sex offender under Megan’s Law.

Before his sentencing, his legal team had argued that Mell was a humble man who fell into “a spiral of depression” brought on by survivor’s guilt over giving up his seat on a fatal helicopter trip with friends, according to a recent report in Gulf News World.

Anthony G. Attrino may be reached at tattrino@njadvancemedia.com. Follow him on Twitter @TonyAttrino. Find NJ.com on Facebook.

Get the latest updates right in your inbox. Subscribe to NJ.com’s newsletters.