The strike was called by three main trade union confederations who are demanding higher wages, benefits and pensions and better working conditions.
General elections are set for May and the right-of-centre government is under pressure.
Brussels, a hub of European government institutions, was particularly hit by the strike's effect on public transport.
Belgium's Brussels Airlines has cancelled all its 222 flights.
European solutions for travellers
In case of difficulty due to air traffic controllers' industrial action, international travellers may have access to alternative, if not longer routes.
The German carrier TUI fly will operate its scheduled Belgian flights from the nearest French and Dutch airports
The high-speed train traffic to London and Paris should be more or less running as usual.
If re-routing via London, they will be sure to make the most of guaranteed visa-free travel to Continental European countries until 29 March 2019 when the UK may leave the EU with a so-called "no-deal", or hard Brexit.
Government under pressure
The Belgian government has been dogged by recent strikes, with elections on the horizon, but also because it shares the capital with the European Union.
Two weeks ago, Belgian farmers, livestock included, demonstrated in Brussels to air their concerns about a freetrade agreement between the EU and Latin America, home of some of the world's prime beef stock.