Air traffic controllers in Spain on Monday launched a staggered four-day strike that could affect around 5,300 flights in the world's third most visited country.
The staggered strike this week was called by the controllers' Usca union for Monday, Wednesday, Friday and Sunday between two blocks of time: 0800-1000 FREE GMT and 1600-1800 GMT.
The Spanish ministry of public works has imposed a minimum service during the strike, which will involve around 70 percent of personnel.
The union will respect this requirement, a spokeswoman told AFP, but will appeal the decision which it claims interferes with the right to strike.
The strike action could affect 5,355 flights, slightly less than a quarter of all scheduled flights over the four days, according to Enaire, Spain's manager of air navigation.
The air traffic controllers are protesting against sanctions imposed by Enaire against 61 controllers in Barcelona after a wildcat strike which paralysed Spanish air traffic in December 2010, affecting more than 200,000 passengers on the eve of the Christmas holiday season, according to authorities.
Usca has called on Enaire to suspend the sanctions, saying in a statement most courts have concluded that there was no "disobedience nor abandonment" of their work stations.
Tourism represents nearly 11 percent of the Spanish economy and 12 percent of jobs.