The employees at the airport in the Belgian capital, which was the target of a deadly attack claimed by ISIS last week, have been identified as supporters of the evil terror group.
Some of the terrorist sympathisers even have security passes which can get them into aircraft cockpits.
The shocking open letter, written by Zaventem airport police officers, comes just over a week after 32 people were killed in twin bombings at the airport and a metro station in the centre of Brussels.
Officers also claim certain people who are suspected of having fought in Syria came to the airport as “fake tourists” to test the airport’s security to plan the deadly attack which killed 14 people.
Airport police officers wrote: “Certain people suspected of having fought in Syria have come to the airport posing as ‘fake tourists’ . We have flagged up their presence but we don’t know if anything was done with this information.”
The letter added that it “was clear scouts had been sent to determine the level of security in order to plan the [Brussels] attacks.”
Hundreds were injured in the terrorist attacks in Brussels
“In the past, certain people’s security passes have been confiscated but, obviously, not everyone’s.
“The suspects are mainly shop assistants, cleaners and baggage handlers.”
Two suicide bombs were detonated in the international airport by ISIS terrorists
The letter went on to call for airport workers being investigated by anti-terror services to be removed immediately and for a more thorough screening of staff.
Belgian security services have come under increasing scrutiny in the wake of the Brussels and Paris attacks.
Belgium, which is at the centre of the investigations into the Paris attacks, has been criticised for failing to tackle extremism in troubled areas such as the Brussels district of Molenbeek.
Much of the small international airport was damaged by the deadly blasts
Brussels airport remains closed and is not expected to start running flights until Saturday.