Hi ClubMan,
Yes, I'm aware of the artifical ripening process used. But I was just saying that once a banana starts to ripen it actually releases ethylene which in turn can cause other unripened bananas (and other fruits) to begin ripening. I found the following at this link: http://pubs.acs.org/cen/coverstory/85/8544cover.html
"In practice, these fruits are often picked green off the tree or plant so they can withstand shipping before they get too soft. Ethylene is such a powerful hormone that if a single banana is ripening in transit from the tropics, the gas can spur a mutiny of ripening among its compadres. Bananas are therefore shipped in containers that contain chemicals such as potassium permanganate that can absorb or inactivate ethylene and prevent any ripening disasters. The green bananas are then exposed to ethylene gas when they are safely ensconced in a local warehouse, a few days before their planned delivery to nearby store shelves."