'Wheel of Fortune' Fires Jim Thornton After Pedophile Chatroom Incident

Jim Thornton is 86'd from "Wheel of Fortune" ... TMZ has learned Sony Pictures Television Studios dropped the hammer Friday afternoon.

A Sony spokesperson tells us ... "Following a thorough investigation, Jim Thornton’s employment with Wheel of Fortune has been terminated, effective immediately."

The firing comes days after TMZ broke the story ... Thornton was flying American Airlines to Los Angeles in May when a passenger spotted him on what she believed to be a chatroom for pedophiles.

You can see in the photos ... disturbing messages mentioned "couple of cute boys and a hot little girl," as well as "All-you-can-eat Boyfett."

There were also several references to "CP" ... often online shorthand for child porn.

Although Thornton has not been charged with a crime, the producers of 'Wheel' moved quickly after conducting their own investigation. Sources with direct knowledge tell us an interim announcer will be heard when the new season begins on September 14, and Thornton's been removed from the show's social channels.

As we previously reported, a passenger on that American Airlines flight spotted his screen, notified a flight attendant who alerted the pilot ... who ultimately contacted authorities.

Law enforcement met the plane when it landed at LAX -- the authorities questioned Thornton about the incident, but he was ultimately free to leave.

Jim's lawyer previously told TMZ the whole thing was seemingly a big mix-up -- she says Jim often visited a suicide prevention chat forum, chat.988lifeline.org, to help people struggling with suicidal ideation.

But Jim claims he had been sent the wrong link and wound up on lifeline.chat, which is for people with pedophilic thoughts.

He claims he left as soon as he realized the mistake, but the timestamps tell a different story -- from the photos, it looks like Jim was in the chat for almost an hour.