Right at the height of the summer travel season, more than 60,000 ground staff and baggage handlers are threatening 24-hour walkouts on Aug. 18 and Aug. 26 that could cripple airports across Spain.
Three large unions, CCOO, UGT and USO, announced the strikes in response to handling companies repeatedly breaking industrial agreements with workers. The strike was sparked, in part, by the decision of a private company at Barcelona's El Prat airport to lay off four workers.
A CCOO spokesman said: "When WFS took over the handling contract at the airport, they guaranteed there would be no redundancies, then shortly afterwards they made four people redundant.
"That is unacceptable. For us it was the straw that broke the camel's back. We've been trying to sit down with the company since July 4, but without success. Industrial action is our only option."
Three of the staff were later rehired by the same company, WFS, but the unions called the action in support of the fourth worker, who remains out of a job.
August is Spain's busiest month for tourism, and thousands of British travelers flock to the sunny nation - the top summer holiday spot for Britons.
The strike will hit extra hard for Spaniards who are already dealing with a troubled economy, where the tourism industry has only just begun to recover after three difficult years.
The Daily Mail reports that union bosses are expected to meet this week to discuss providing "minimum services" to travelers.
The first strike coincides with the arrival of Pope Benedict XVI in Madrid for World Youth Day celebrations. A union representing Madrid's underground workers, UGT-Metro, has also called a strike that day in an unrelated industrial action protesting cuts to wages as part of government austerity measures.
Up to a million pilgrims are expected to flock to the Spanish capital for the three-day papal visit.