The rocker left his first wife Alana Hamilton for model Emberg in the 1980s, but the union fell apart while she was pregnant with their daughter, Ruby, who was born in 1987.
Stewart spent years playing the field before deciding he wanted to reconcile with Emberg, and he arranged for a romantic proposal with a banner trailing from a plane.
In his new autobiography, serialised in Britain's Daily Mail, he writes, "I decided to propose to her. That was the obvious solution, only I'd been too foolish to see it. But, if it was going to work, I'd need a big romantic gesture - something she'd find charming and irresistible.
"I knew that little prop planes often buzzed above the... beaches, trailing advertisements. What if Kelly were to look up from her boat and see my marriage proposal written in the sky? Could it get any more sweetly romantic than that?
"I organised a plane and a banner for early Sunday afternoon, which I figured was the best time to be sure of catching Kelly's attention. And I told the company I wanted the banner to say: 'Kelly - will you marry me? Rs.' That would do it, wouldn't it?"
However, Stewart was left trying to cancel his romantic gesture after he met Rachel Hunter, who went on to become his second wife, the night before the proposal.
He recalls, "Feeling far happier, I went out to dinner that Saturday with Sylvester Stallone. Afterwards, we went on to an L.A. nightclub called the Roxbury. And across the floor of the Roxbury, I caught sight of a woman...
"I had to introduce myself to her. And then I had to convene a small party back at my place so that I could invite her along with her friend and get to talk to her properly. Rachel Hunter did come and we did talk; and by the time she went home, it seemed blazingly apparent to me that this was the person I wanted to dedicate the rest of my life to.
"I awoke the next morning glowing with excitement. In the midst of my euphoria, it was at least 10 minutes before I remembered, with a cold feeling abruptly passing across my kidneys, that I'd arranged an airborne marriage proposal for that lunchtime.
"No problem. I'll cancel it. I'll call the advertising company, I thought."
However, the star's efforts to scrap the proposal didn't go smoothly: "The phone rang and rang. I hung up and tried again. It was Sunday: everybody had packed up and gone. This was awkward. I'd hired a plane to carry a banner saying 'Marry me'. I couldn't very well hire a second plane saying: 'Sorry - scratch that. Rs.'
"What was I going to do? Pray for a hurricane? Get out there on a boat with a large gun and shoot the f**ker down? No. What I was going to do was spend Sunday wincing in anticipation, with my fingers crossed. And what do you know? My grand, absurd and doomed marriage proposal went up, fluttered across the sky and came down again, entirely unseen by its intended recipient. Truly, there is a God."
Stewart's 16-year marriage to Hunter ended in divorce in 2006, and he wed third wife Penny Lancaster-Stewart in 2007.