* Unions, airport operator reach preliminary agreement
* Accord must still be voted on by workers
* Strike called in late February to protest privatisation
(Adds prime minister comment, shares)
MADRID, March 16 Spanish airport operator AENA and unions reached a preliminary agreement to call off 22 days of strike action between April and August, AENA said on Wednesday, averting disruption during peak holiday season.
The agreement takes on board unions' concerns over labour conditions and job security for the state airport operator's nearly 13,000 staff in the face of a planned government privatisation, union representatives told national radio.
"The agreement was reached after nearly 20 hours of talks," AENA said in a press release, noting the accord still had to be voted on by workers.
Prime Minister Jose Luis Rodriguez Zapatero said the agreement meant airports would work at normal capacity during the Easter and summer holiday periods.
Around 77 percent of tourists arrive in Spain via air travel, bringing more than 190 million passengers through Spanish airports every year, he said.
However, one analyst expressed caution on the provisional agreement.
"We welcome this announcement, albeit we stress that it is a pre-agreement that needs to be confirmed by workers in a poll," said Eduardo Coelho, analyst at broker BPI.
Spain said in December it wanted to partially privatise the state airport operator, which it says could be worth up to 30 billion euros, alongside its state lottery as part of plans to reduce the national debt.
Air traffic controller strikes in early December stranded thousands of passengers and caused chaos at Spanish airports.
International Airlines Group (ICAG.MC), the company formed by the merger of British Airways and Iberia, was 0.4 percent lower at 2.6 euros while no-frills airline Vueling VULG.MC rose 1.9 percent.