Jefferson Airplane in 1989 (Chris Walter/WireImage)Paul Kantner, co-founder and one of the guiding creative forces behind both the Jefferson Airplane and Jefferson Starship, died Thursday of multiple organ failure at age 74 after suffering a heart attack this week. Kantner’s former band mate Marty Balin posted a message paying homage to his old friend after news of his passing was announced, and now the other surviving members of the Jefferson Airplane’s classic lineup have penned their own tributes.

Singer Grace Slick, who joined the Airplane prior to the band’s classic second album, 1967’s Surrealistic Pillow, and also co-founded the Jefferson Starship with Kantner, posted a brief message about Paul on her official Facebook page. “Rest in peace my friend. Love Grace,” she writes. Slick and Kantner also had a romantic relationship during the late 1960s and early ’70s, and had a daughter together, China Kantner, in 1971.

Founding Jefferson Airplane guitarist Jorma Kaukonen, meanwhile, has written a lengthy homage to Kantner that appears on his official website. Kaukonen recalls that he was introduced to Kantner in 1962, and notes that prior to the Airplane’s formation, they “played the same little dusty, smoky rooms…struggled to be heard over the hiss of espresso machines…and loved every moment of it.”

Jorma explains that the Jefferson Airplane was “an amazing aggregate of personalities and talent,” and credits Paul for being “the catalyst that made the alchemy happen.”

Describing Kantner’s role in the group, Kaukonen writes, “He held our feet to the flame. He could be argumentative and contentious…he could be loving and kind…his dedication to the Airplane’s destiny as he saw it was undeniable.”

Jorma also reveals that he and Paul had been estranged for a while until they rekindled their friendship last year after Kantner accepted an invite to have dinner with him in San Francisco.

Kaukonen adds, “Friends are always good… you can’t have too many of them. That said, the old ones share that wondrous gift of knowing you when you were young. You can’t buy that.

He finishes his tribute by telling Paul, “I will miss your presence on this plane…Ride free to the end of the earth my old friend…I will not forget you!”

Lastly, founding Airplane bassist Jack Casady posted a message on his own Facebook page paying tribute to Kantner. Casady says Paul was “a true San Francisco original,” and goes on to recount a favorite memory of his old band mate.

Jack writes that he remembers “looking over at Paul on stage in Golden Gate Park [during the] late 1960s and seeing him with his Rickenbacker 12 string guitar raised over his head in revolutionary stance calling out to ‘his’ people assembled in the park!!! Great times…”

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