Air traffic controllers in 11 EU countries will take industrial action on Wednesday in protest against plans to create a single airspace for the bloc, unions said.
Controllers in Belgium, the Czech Republic, Italy, Portugal and Slovakia will work to rule, Francois Ballestero of the European Transport Workers' Federation said Tuesday.
Other forms of industrial action including public information campaigns will take place in Austria, Britain, Bulgaria, Hungary and Latvia, he said.
France is already being hit by a three-day strike that started on Tuesday over fears that the EU plans will affect safety and working conditions.
The European Commission will present proposals later Tuesday to speed up the reform of Europe's air traffic control system as part of a decade of difficult efforts to create a "Single European Sky."
"This day of action will highlight the social cost of the reforms of a 'Single European Sky'," Ballestero told AFP.
"The commission is planning rules that will further liberalise the sector and affect job numbers," he added.
The Brussels-based ETF represents 250,000 civil aviation sector employees, including 25,000 air traffic control workers, in the 27 countries of the EU.
The EU says the single sky plan could triple its airspace capacity, improve safety ten-fold, reduce pollution by 10 percent and cut air traffic management costs by 50 percent.
Fragmented country-by-country air control is estimated to bring extra costs of close to five billion euros (6.6 billion dollars) a year to airlines and passengers, adding 42 kilometres (26 miles) to the distance of an average flight, thus also harming the environment and causing delays.
The United States controls the same amount of airspace with mote traffic at almost half the cost.