A walkout by air traffic controllers over pay closed air space around Madrid on Friday at the start of one of the country's busiest long weekends, state-owned airport authority AENA said.

Air space around the holiday destinations of Ibiza, Menorca and Palma, Mallorca were also closed after Spanish air traffic controllers staged a walkout in unofficial strike action, Spain's airports authority AENA said.

Air space around the Canary Islands was also closed, airline Iberia said.

"The captain came out to say Spanish air space had suddenly shut, with no prior warning," one passenger stuck in a plane in Palma airport told national radio.

AENA and the air traffic controllers' union have been locked in dispute over pay and working conditions for months.

"I suppose people have had enough," air traffic control union USCA spokesman Daniel Zamit told CNN+. An USCA spokesman told Reuters the controllers were not on official strike.

Controllers claimed sick leave and started to abandon their posts around 1600 GMT, AENA said in a statement. The authority urged passengers to stay away from the airports in question.

"This irresponsible decision is causing serious disturbances in air traffic across Spain," AENA said.

Airline Iberia estimated air space would remain closed until 0100 local time (2400 GMT).

Madrid's Barajas airport is the country's busiest and a hub for both international and national flights. It is also the base for national carrier Iberia , which last week completed a merger with British Airways.

Earlier, Spain's cabinet approved government plans to sell off 49 per cent of AENA as it tries to assure markets it can meet its deficit cutting objectives.

Air traffic controllers' relatively high salaries and short working hours have raised hackles in the Spanish media as the country applies painful public sector pay cuts as part of austerity measures to drive down the deficit. – Reuters