A total of 92 percent of the country’s 2,300 controllers with a right to vote cast ballots and almost all, 98.25 percent, voted in favour of the strike, the Union of Air Traffic Controllers (USCA) said in a statement.

The date for the strike is expected to be announced on Wednesday but since the union must give a 10-day warning, the earliest it could come is mid-August, the busiest time for the country’s key tourist industry.

USCA said a strike “was the only alternative to denounce their labour conditions and, consequently, air traffic security.”

The controllers, who are employed by state-run airport management firm AENA, are angry over a government decree on working conditions announced last week which would reduce rest periods and cut generous overtime benefits.

Transport Minister Jose Blanco earlier said he saw “no reason” for a strike and called on the controllers to adopt the new rules “without delay.” He also vowed to maintain minimum services during the walkout.

The government’s decree on working conditions came six months after it curbed what it described as the “millionaire salaries” enjoyed by the controllers, calling their high rates of pay and benefits “incomprehensible privileges”.

The salary curbs followed outrage across Spain after the public disclosure that some controllers were earning more than 600,000 euros (785,000 dollars) after overtime pay was added to their basic salary.

The government last month also vowed an investigation into the sick leave taken by almost half the air traffic control staff at the control centre in Barcelona in what it suspects is an undercover strike.

It said it may deploy the military to replace Barcelona air traffic controllers on sick leave.

The government this year has introduced tough austerity measures to rein in the massive public deficit as the country emerges from a recession that began in 2008.