Staff at loss-making Spanish flag carrier Iberia are set to begin a five-day strike at midnight tonight.
It will ground over 1,000 flights, which will cost the airline and the struggling national economy millions of euros.
Workers, including baggage handlers, pilots and air stewards, will hold three five-day strikes in February and March to protest management plans to axe 3,807 jobs and cut salaries.
Iberia has cancelled 415 flights between Monday and Friday, although a total of around 1,200 flights operated by various airlines will be grounded because of the lack of handling services at Spanish airports.
The airline said 70,000 passengers would be affected by the first strike and that it had placed some customers on different flights, including those operated by different airlines, while proposing refunds and alternative travel dates for others.
Iberia, which merged with profitable British Airways in 2011 to form the International Airlines Group, reported a loss of €262m in the first nine months of 2012.
The first strike, from February 18 to Februray 22, coincides with school holidays in Britain, Spain's biggest source of tourists.
Transport Minister Ana Pastor pleaded last week for the airline and labour unions to strike a deal, warning of the damage the strikes could do to the Spanish economy. "We can't allow Spain to lose more than €10m a day because that kind of hit is going affect all of us," Pastor said.
Tourism accounts for around 11% of Spanish economic output and is one of the country's very few growth sectors in a prolonged recession that has pushed the unemployment rate above 26%.
Spain's Transport Ministry has guaranteed skeleton services to cover the strike. Iberia said 90% of long-haul flights would take off and domestic services would be worst affected, with almost half grounded between Monday and Friday.
Airports across Spain will also be disrupted by union-organised demonstrations for several hours on the first and last days of the strike. Workers will hold a street protest in central Madrid on Wednesday evening.
Iberia is just one of several companies in Spain, including Vodafone and bailed-out lender Bankia, to lay off workers. It is fighting an uphill battle against low-cost operators, a depressed domestic economy and competitors that are in better shape after having already gone through restructuring processes.
"We've got a bad image. Flying with us is a lottery. That's why our primary objective is to guarantee good service and punctuality when travelling with us," Iberia chief executive Rafael Sanchez-Lozano has said.
The airline said it had found alternative flights for 60,000 customers whose journeys would be affected by the strike, while others had been offered refunds or flights on different dates.
Analysts said the total fifteen days of strikes could cost Iberia between €50-100m of losses. Two further strikes are planned for March 4 to March 8 and March 18 to March 22.