David Batey and Luis Restrepo, who both work at TG Lynes in Enfield, with a phobia of flying and heights will face their fears by wingwalking at 135mph for charity.
They will be strapped to the wings of a plane to fly above the fields of Bedfordshire in September and raising money for Teens Unite, which supports young people fighting cancer.
Luis said: “On a scale of one to 1,000, I’d say my fear of heights is 1,000. If I go up a small ladder and look down I need help. I just glue myself to it. I went on a rollercoaster 20 years ago and felt like I was having a heart attack.
“I get goosebumps just thinking about the wingwalk. My family aren’t happy I’m doing it, but I wanted to do something completely out of my comfort zone to help a great charity.
“I’m preparing as much as I can by watching videos of other people wingwalking, but it’ll get more nerve-racking as the day approaches.”
David added: “I don’t like flying and haven’t been on a plane in more than five years. I will be extremely nervous, there’s no doubt about that, but once I commit to something there’s no turning back.
“It’s all for a good cause and I’m hoping I can somehow enjoy the experience!”
Andrew Ingram, managing director at TG Lynes, said: “I am full of admiration for Luis and David for facing their fears, pushing the boundaries and taking on this terrifying challenge.
“I hope people dig deep and support Teens Unite, which is a fantastic local charity we have had the pleasure of working with over the last 12 months.”
TG Lynes also supported Teens Unite with £7,500 worth of product and labour through its Helping Hands campaign last year.