A nationwide strike will be held on Monday 13 January, with workers from all sectors taking to the streets. Here's what you need to know about the action and its impact.
A more recent article was published with the latest information on Monday 13 January. Follow for live updates here.
Trade unions representing the transport sector, the education sector, the national prison service and more have invited its members to take part in a national strike to protest the next government's probable pension reforms.
"The measures on the table represent unprecedented attacks on all working men and women," trade union CSC said. "Wage freezes, indexation reform, longer working hours and more precarious contracts, austerity, cuts to public services and ecological investments: nothing will be spared for Belgians, not even pensioners."
Strike participants will gather at Place de l'Albertine in Brussels at 10:00 on Monday morning, but the official action kicks off from 22:00 on Sunday until 22:00 on Monday. Huge numbers have prompted the Flemish socialist trade union ACOD to express concern about transporting all participants to the protest. "The subject is very heated, but we won't have everyone in Brussels," according to ACOD president Chris Reniers.
Multiple services across the country will grind to a halt as a result of the demonstration.
Flights delayed and cancelled
Brussels Airport expects a "major impact" on Monday. At least four out of ten flights scheduled for Monday at Brussels Airport have been cancelled, the airport announced on Sunday.
A significant number of employees in baggage handling and security staff are participating in a union action. The airport warns that additional flights may still be affected. Airlines are directly informing passengers of impacted flights.
For flights that are still operating, passengers should arrive on time: two hours before a flight within the Schengen Area and three hours before a flight outside the Schengen Area. Passengers planning to travel to Zaventem by train should also expect severe disruptions due to the union action affecting the railway.
Half of the European flights chartered by Brussels Airlines will not be taking off on Monday due to the nationwide strike, the Belgian airline announced on Saturday.
"This demonstration is likely to have a major impact on the baggage handling companies at Brussels Airport, among others. The airport management has therefore asked us to cancel a large number of flights as a precaution," explained Brussels Airlines in a press release. Passengers affected by these cancellations will be contacted by Brussels Airlines and offered alternative flights.

The departure hall of Charleroi Airport pictured during a strike. Credit: Belga/ Nicolas Maeterlinck
Brussels South Charleroi Airport (BSCA) warned of potential delays for both departures and arrivals on Monday in a message posted on Facebook on Saturday. Travellers with flights scheduled on Monday are advised to arrive two hours before their departure times.
Meanwhile, unions representing shipping pilots say the impact on ferries will be "limited".
Adapted public transport
Train services will be heavily disrupted on Monday, railway operator SNCB has confirmed. Along with partner company Infrabel, SNCB is preparing an adjusted rail service based on non-striking staff.
The railway strike will begin on Sunday evening at 22:00, with normal train services expected to resume on Tuesday morning.
During the strike, SNCB will be running only one out of three IC trains. Four out of five L and S trains will be cancelled. Virtually no peak hour (P) trains will run.

A previous railway strike in 2016, at the Antwerp Central train station. Credit: Belga / Nicolas Materlinck
The impact may vary by province, noted SNCB spokesperson Bart Crols. Railway companies are advising students with exams to plan ahead.
More details of the reduced service will be available on the SNCB website from Saturday afternoon.
Brussels public transport operator STIB is also expecting serious disruptions. It is trying to guarantee at least part of its service but has asked passengers to find alternative modes of transport where possible.
As of Sunday evening, STIB stated that these lines should be operating:
- Metro: Line 1 (extended from Gare de l’Ouest to Erasme)
- Trams: 4, 7, 8, 9, 10, 51, 92, T-bus 9 (extended from Simonis to Gare de l’Ouest / Weststation) and T-bus 92 (between Lancaster and Fort-Jaco).
- Bus: 12 (serves all stops on its itinerary), 36, 48, 50, 53, 59, 71, 73, 87 (extended from Simonis to Etangs Noirs)
STIB said on Sunday that this information cannot be confirmed until Monday morning, in real time. "For the time being, we cannot say with certainty which lines will be operated. Some bus lines could possibly be added to the list."
No disruptions are currently expected by the Flemish public transport company De Lijn, while its Walloon counterpart TEC will communicate on the extent of the disruption on Monday morning.
'Don't travel to Brussels by car'
Brussels police are expecting major traffic problems in the centre of the capital on Monday. They advise against travelling to Brussels by car, although alternatives will be very limited given the disruption to public transport.
"It's difficult to estimate the scale of the traffic problems because many people will be working from home or taking time off to look after their children," says a spokesperson for the Brussels-Capital-Ixelles police force. Around a hundred buses are expected to bring demonstrators from the provinces to Brussels.
"We'll see on Monday how many people are actually there, but from the information we're getting, we can expect a lot of people." The buses will drop the demonstrators off at around 9-10:00 at the Place de l'Albertine, before moving on to Boulevard Albert II. The procession is due to converge on Place Poelaert.
No rubbish collection
Brussels residents have been warned that their rubbish may not be collected on Monday. Nevertheless, Bruxelles-Propreté (the Brussels agency responsible for public cleaning) have advised residents and businesses in impacted areas to stick to the normal schedule.

Credit: Belga / ImageGlobe
If the bags are not collected, it is recommended to leave them in front of the residence, since catch-up rounds will be organised "depending on available human resources".
Other services may also be affected, including container waste collections from businesses and apartment complexes, Recyparks (the dump), chemical waste collection and home collections of bulky items.
Bpost support strike
Belgium's postal services have also lodge a strike notice, but the extent of the impact is still unclear.
Disruptions to postal delivery services are expected on Monday due to the overall strong support from postal union members.
Bpost has acknowledged the impact but aims to minimise it, stated bpost spokesperson Mathieu Goedefroy.
More than 20,000 teachers to take part
Over 20,000 teachers have registered to take part in the strike, according to Koen Van Kerkhoven, head of the Christian Teachers' Union. The planned pension reforms "contain too many elements that we are worried about," he said.
A survey published by the Association of Flemish Education Managers (VLVO) on Friday indicated that 35.51% of schools in Flanders will "probably" close on strike day.
Based on results from 654 school principals surveyed, primary schools seem to be predominantly affected. Across all education levels, 24% of respondents said lessons would not continue and 8% said school may close.
In addition, parents have expressed understanding for the striking teachers, according to VLVO. 23% of school principals say they have received considerate responses from parents.

Credit: Belga
The French-speaking students' federation (FEF) has on called for the postponement of higher education exams scheduled for Monday due to the impact of the strike on both public transport and education workers.
"While the FEF firmly supports the union mobilisations against the future Arizona government, it calls on higher education institutions to demonstrate responsibility by postponing the exams scheduled for that day," it stated on Friday. "The announced disruptions risk preventing many students from going to their exam locations, thus compromising their academic success."
Prisons on strike - again

Credit: Belga/ Nicolas Maeterlinck
Prison staff, a sector that is repeatedly on strike, are also taking part. Their action will last from 22:00 on Sunday until 06:00 on Tuesday.
Trade unions, who say staff are at risk of "antisocial and populist pension measures," are expecting a strong turnout.
"The determination is all the more because in addition to difficult working conditions and insufficient salaries, there is now the prospect of a lower pension at the end of a difficult career," said ACOD federal secretary Robby De Kaey.
Rare strike from defence sector
A rare appearance will also be made by the defence sector union on Monday. A delegation from the Free Public Service Union (SLFP) announced on Sunday it will represent the defence sector in Monday's pension reforms protests. This is despite the new government having already indicated it will increase defence spending.
A union spokesperson believes that investing in new equipment like F-35 aircrafts and ships without adequate personnel is a waste of public funds and poor management.
New pension conditions will result in staff losing between €300 and €800 per month and working eleven years longer, the spokesperson added, saying the situation is "lose-lose".