The protest is aimed against what the officers call a "chronic shortage of staff". If no settlement is reached, the work-to-rule could last until the end of August.

At present 61 federal police officers work at Charleroi Airport where the low cost airline Ryanair is the biggest operator. The police union NSPV says that a workforce of 77 is really needed.

The union also points out that ten of the present staff don't have the right training to carry out immigration checks. These officers will now be replaced, but the move won't solve the staff shortage.

Passengers travelling out of Charleroi are being advised to turn up well on time. The police union says passengers could face a wait of 2 and a half hours in the immigration queue.