Strikes by pilots in Germany and Portugal are threatening to add to the European disruption caused by the recent industrial action by British Airways.
The annual congress of the 105,000-strong International Association of Airline Pilots Associations voted to back a planned stoppage by pilots at Germany's Lufthansa, Europe's largest airline.
Meanwhile Portugal's economy minister warned that the planned strike by TAP pilots will hurt the tourist industry as it tries to recover from a drop in arrivals last year.
They have announced a strike between March 26-31 to press their claim for higher pay.
The state-owned airline says it has 1,500 flights scheduled for those six days and around 150,000 passengers may be affected.
"Our tourist sector is coming out of a very deep crisis. (This strike) is not good for it," economy minister Jose Vieira da Silva said.
Tourism accounts for about 8% of Portugal's gross domestic product, and 12 million people visit the country each year.
Hotels on the Algarve, the main tourist destination, reported hotel bookings were down up to 12% last year amid the global economic downturn.
TAP has offered its 800 pilots a 1.8% pay increase this year but their union wants at least 5.6%.
It has a fleet of 51 Airbus planes and flies to 58 destinations in 27 countries in Europe, Africa and North and South America.
Although crews at each of the carriers have specific reasons for going on strike, the underlying causes are the financial difficulties faced by the airline industry and the cost-cutting airlines have had to resort to in an effort to main competitiveness.