I've received an e-mail from Airport IT Services, they've decided to no longer publish cargo flights information to Public Flight API (which this website uses) nor the the Schiphol Website.

That seriously sucks for us spotters, especially now that most (interesting) flights that come into Schiphol are cargo flights due to the pandemic.

I'll keep this blog updated if there's any further info.

For now, keep your eyes on other sources (Scramble Forum, Flightradar 24 and your trusty old eyeball mk.1).

Update 22-06-2020: As of this afternoon cargo flights are back, which is excellent news! However GA and businessjet flights still appear to be missing. I've asked the API support team for confirmation.