Gisele Bündchen felt as though she had hit "rock bottom" when she began experiencing panic attacks.
The 38-year-old supermodel - who is married to NFL star Tom Brady, with whom she has Benjamin, eight, and Vivian, five - admitted last week she struggled with anxiety toward small spaces throughout her 20s, and has now revealed the condition was triggered by a shaky plane journey that left her feeling "powerless".
She said: "That was definitely rock bottom for me.
"It started all in a little plane. I was in Costa Rica and I was flying a six-seater plane and the plane started shaking like a little leaf. I was, like, completely a sense of powerless, you know?
"I'm the kind of person who likes to have things under control. That was definitely an out-of-control moment and it kind of started this kind of fear of being in small spaces."
Gisele's anxiety grew stronger over the years, and before long she was unable to be in any small spaces, and was forced to take the stairs to her ninth floor apartment because she wouldn't get in the elevator.
She added: "So it started with a little plane ride but then it became tunnels, subways, elevators. I lived on the ninth floor in an apartment and I would go up nine floors of stairs because I was scared that I would suffocate. It was crazy. My world just kept getting smaller and smaller."
The blonde beauty has chosen to open up about her struggle in order to help other people in her situation, so they don't have to "feel alone".
Speaking during an appearance on 'Good Morning America' on Tuesday (02.10.18), she said: "The reason why I wanted to share this story that to me is very private and puts me in a very vulnerable position in a way is with the hopes that people don't feel alone.
"It was like I was trapped and I couldn't breathe even outside on my own balcony. From that moment on, I realised that my life needed to change."