on Apples shop website I can‘t see a 16Gb Macbook Air.

Did I miss it? Or can‘t I see it if there is no availability anymore? Anyone a link?

It's a custom build option, I'm guessing you're onto the page with the couple of preset options? If you click "select" on a model you get a second page that lets you customise stuff like RAM and SSD.

This link might work: https://www.apple.com/shop/buy-mac/macbook-air/space-gray-ap...

Just select it and you'll see an option to upgrade to 16G (which adds a whooping $180 to the price): https://www.apple.com/us-hed/shop/buy-mac/macbook-air/space-...