The employees of Menzies Aviation will go on strike for better salaries.
Checking in passengers, handling luggage and moving planes on the airport will be affected, so there can be serious delays.

As more news becomes available, we will publish it here.

Update 9 May: Schiphol has published a list of the affected airlines on this website.

In the afternoon it appears the effects of the strike are rather limited (though some flights have delays). Only about 20% of the workers are on strike.

Update May 11: The strike has ended.