PayPal: express checkout pay without account

Is it possible to do an express checkout payment in PayPal without an account?

I remember that I saw it somewhere, but I don't remember where. Once a time in PayPal there was a link under "Create a PayPal account".

Yes, that's certainly possible.

Simply set SOLUTIONTYPE parameter to Sole in your initial SetExpressCheckout API call (SOLUTIONTYPE=Sole). Optionally you can also specify LANDINGPAGE=Billing for the billing page to be forced.

Note: In order for SOLUTIONTYPE=Sole to work, you must have 'PayPal Account Optional' set to 'On' with the 'Website Preferences' section of your PayPal account.
Profile > My selling tools (or: My selling preferences) > Website Preferences > Update > PayPal Account Optional: On.

EDIT:

As mentioned in one of the comments, it's possible this may only work if you add the LOCALECODE=us parameter too.