Carrie Underwood looks back on sweet memories with late legend Brett James

Carrie Underwood took a heartfelt trip down memory lane in an emotional tribute to Brett James after the news of his tragic passing.

The Grammy-winning songwriter died in a plane crash on September 18, in Macon County near Franklin, North Carolina at the age of 57.

Shortly after James' passing was confirmed, Underwood, 42, took to her Instagram to honour the Jesus, Take the Wheel hitmaker.

"Some things are just unfathomable," she began the lengthy message, alongside three pictures of them captured over the years. "The loss of Brett James to his family, friends and our music community is too great to put into words."

"Brett was the epitome of 'cool,'" the American Idol winner wrote and went on to fondly recall two memories with the legendary musician.

One of her favourite moments was hearing him sing Cowboy Casanova, because "a sassy girl anthem should’ve sounded ridiculous coming from a macho dude like him, but somehow, he even made that cool."

In another memory, the Remind Me singer recounted a songwriting session where James came in with most of the song already written.

Though she contributed some melody and finishing touches, she told him she didn’t feel right taking equal credit. But James insisted they split it evenly, showing the generosity and humility that defined him

"Brett loved the Lord. Which is the only comfort we can hold on to now," the country singer continued. "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. 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," she wrote before concluding. “Love you, man. I’ll see you again someday.”

Underwood and James collaborated on the Grammy-winning song Jesus, Take the Wheel as well as Cowboy Casanova.