Joni Mitchell recorded "This Flight Tonight" for her 1971 album Blue. She wrote the song, she sings it, and she produced it.
In 1973, Nazereth covered the song for their album Loud 'n' Proud. They really rocked it up, and Canadian rock radio play it all the time.
So we have a Canadian artist covered by a Scottish band, and this Scottish band's cover would influence an American band with a Canadian connection. Nancy Wilson revealed that the guitar riff for Nazareth's version of "This Flight Tonight" inspired the riff for the Heart song "Barracuda".
Ann and Nancy Wilson are American, but they fell in love with Vietnam draft dodgers who ended up in Vancouver where they recorded Dreamboat Annie. That album qualified as Cancon because it was recorded in Canada by artists residing in Canada.
And that's how Joni Mitchell connects to Heart.