Gaines was an original cast member of a school play called Hairspray, which would become a Broadway musical a few years later. Shortly after the play was performed, JoJo Billingsley was sent to her from Ronnie Van Zant to invite Cassie to joining Lynyrd Skynyrd as a backup singer. She had never heard of Skynyrd at the time, so JoJo lent to her a copy of the band's first two albums: (Pronounced 'L?h-'nérd 'Skin-'nérd) and Second Helping. In late 1975, Cassie, JoJo, and another girl named Leslie Hawkins became The Honkettes, a female gospel vocal trio for Skynyrd.
On October 20, 1977, a plane carrying the band between shows from Greenville, South Carolina, to Baton Rouge, Louisiana, crashed outside ofGillsburg, Mississippi. The crash killed Ronnie Van Zant, Steve and Cassie Gaines, assistant road manager Dean Kilpatrick, as well as pilot Walter McCreary and co-pilot William Gray.
On February 15, 1979, Steve's and Cassie's mother, also named Cassie LaRue Gaines, was killed in an automobile accident near the cemetery where Steve and Cassie are buried. She was buried near her children.