Flights from Britain to Spain are likely to be affected as strikes begin around Europe.
One of the largest demonstrations is expected to take place in Brussels, where the walkout is tipped to be the biggest there since 2001.
The European Trade Union Confederation (ETUC) estimates as many as a 100,000 workers from more than 30 countries will march towards the European Commission to shout: "No to austerity". The organisation's general secretary, John Monks, said his members were fed up with paying for a financial crisis that was caused by the banking sector.
"We will demonstrate to voice our concern over the economic and social context, which will be compounded by austerity measures," he said.
Unions said 23 million jobs have been lost across Europe since the global downturn began.
Governments across the EU have been under increasing pressure to reign in public spending and many of them have introduced reforms to the labour market and pension systems.
Parallel protests will also take place in other capitals such as Madrid, where a general strike began early today. Labour reforms were being pushed through by Spain's Prime Minister as part of plans to save Europe's fourth-largest economy from a bailout - like the one that saved Greece from bankruptcy.
The stop-work action is likely to cause widespread disruption to the transport system - with airlines likely to be badly affected.
Iberia said it expected to operate only 35% of its scheduled flights as some air traffic controllers and ground crews take part in the strike.
Unconfirmed reports indicate French seaports will be closed between October 1 and October 3, with work stoppages of at least 2 hours each today.
Every protest will be watched carefully by Europe's governments to see just how many people the unions can muster.
A smaller than expected turnout would suggest unions do not have the support or the backing to call more strikes.
On the other hand, big numbers could indicate that Europe is facing a winter of discontent.
Sources: AirNews, BBC, BDP International