Protesters clashed with police at Madrid's international airport as ground staff and cabin crews for Spain's Iberia began 15 days of strikes to protest plans to lay off 3,800 staff.
The company, which is looking to cut jobs after it reported substantial losses last year, says the stoppages will lead to more than 1,200 flight cancelations over the next three weeks, including 236 the first day.
Police used batons to push back hundreds of protesters as they tried to enter the terminal at midday. There were no immediate reports of injuries.
Other demonstrations took place at airports around the country.
A government decree on minimum services guarantees 90 percent of long-haul flights, 61 percent of medium-haul and 46 percent of domestic flights on stoppage days.
Unions representing most Iberia workers, but not pilots, have called the strikes between Feb. 18-22, March 4-8 and March 18-22.
The company says it has found seats on other flights for most of the 70,000 passengers affected.
Iberia, Lineas Aereas de Espana S.A., claims economic difficulties oblige it to make layoffs. The government has called on the company and unions to reach an agreement and end the strike.
Iberia merged with British Airways to create International Airlines Group in 2011.