James, 57, was one of the three people aboard a single-engine Cirrus SR22T when it went down "under unknown circumstances in a wooded area".
All three passengers were killed in the crash which occurred near Macon County Airport, authorities said.
Flight tracking data shows the plane took off from an airport in Nashville.
James earned a Grammy Award for Best Country Song for Jesus, Take the Wheel, recorded by Carrie Underwood.
Reacting to the news, Underwood called his death "just unfathomable".
The song, which also received a nomination for Song of the Year, became a defining hit of both their careers.
"Brett was the epitome of 'cool'," Underwood said.
"My favorite songs to sing of ours are the ones that he or we wrote about Jesus because the thoughts and feelings behind them are so genuine and pure."
She added, " I won't ever sing one note of them again without thinking of him. Brett's passing is leaving a hole in all of us that I fear won't ever go away."
James also penned songs for a wide range of artists including Taylor Swift, Kelly Clarkson, Bon Jovi, and Jason Aldean.
Aldean, who recorded The Truth, written by James, said he was "heartbroken".
"I had nothing but love and respect for that guy and he helped change my life. Honored to have met him and worked with him. Thoughts and prayers going out to his family," Aldean said.
Paul Williams, president of the American Society of Composers, Authors and Publishers (ASCAP) praised James as "a songwriting force of nature", noting that he wrote more than 500 songs across genres.
"He wrote big hits but had an even bigger heart," Williams said.
James was inducted into the Nashville Songwriters Hall of Fame in 2020 and won the ASCAP songwriter of the year in 2006 and 2010.
The National Transportation Safety Board, which investigates air accidents, will lead a probe into the crash.
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