There's a direct train connection between Amsterdam Schiphol Airport and Brussels (200 km, 1.5 hours by Thalys).
And still, @klm operates 4 return flights Amsterdam-Brussels today.

https://sfo3.digitaloceanspaces.com/cdn.mastodon.energy/media_attachments/files/111/079/967/873/195/850/original/04bf307445eab697.jpg