( CNN ) -- Iberia ground and cabin crews Monday began what they said was the biggest strike in the airline 's history , but the company countered that it had already re-assigned most passengers to other flights to reduce airport chaos . Five people were arrested during the strike for going beyond a police line at Madrid 's Barajas airport , a government spokesman told CNN . Earlier , Iberia said in a statement that it had found other flights for 60,000 clients and will give ticket refunds to another 10,000 . But Iberia canceled 415 flights this week , about 40 % of its total , and three smaller airlines for which Iberia provides ground services canceled an additional 800 flights . Most routes -- within Spain , or to nearby destinations in Europe or much longer distances -- were operating , but in many cases with fewer than the normal daily number of flights . The unions are protesting layoffs , salary cuts for many of the remaining staff and company downsizing that has already seen elimination of flights from Madrid to Athens , El Cairo and Istanbul . In April , Iberia will also stop flying from Madrid to Havana , Santo Domingo , Montevideo and San Juan de Puerto Rico . Iberia has announced 3,800 layoffs , about 19 % of the staff , part of an effort to reduce losses , which were more about $ 350 million last year . Ground crews and in-flight attendants announced 15 days of strikes , during three weeks Monday to Friday , starting Monday . Pilots are not on strike this week but are due to join in for next strikes , for the weeks of March 4 and March 18 . Union leaders call it the biggest strike in Iberia 's history because it 's the first time that all three units -- pilots , cabin crews and ground personnel -- have joined forces to strike and it 's the first time so many days of strikes have been announced at one time . Iberia called the situation `` totally normal '' on Monday , given the strike . But Manuel Atienza , of the General Workers Union ( UGT ) said the strike will have more impact as it continues , because overloaded ground crews , even while complying with legally-mandated minimum services , will fall farther behind on tasks like baggage handling . Unions say that Iberia , which merged with British Airways in 2011 , has been suffering ever since as the junior partner , while the majority shareholder British has expanded . Iberia pilots last year went on strike when Iberia created a low-cost carrier called Iberia Express . It and two other airlines that get ground services from Iberia - Air Nostrum and Vueling - also canceled fights this week .
Iberia said it had found other flights for 60,000 clients and will give ticket refunds to another 10,000 . The airline has also been forced to cancel more than 100 flights, including some of its most popular routes. Iberia pilots last year went on strike when Iberia created a low-cost carrier called Iberia Express .