Flights were disrupted Friday as pilots working for the Portuguese airline TAP began a 10-day strike as part of their dispute with the government.
One in three flights were cancelled, a spokesman for the state-owned airline told AFP, adding however that at least 10 percent of its 300 scheduled flights were expected to run.
The pilots accuse the government of reneging on an agreement to set aside between 10 and 20 percent of TAP's capital for employees in its planned privatisation and of not reinstating seniority bonuses frozen in 2011.
Portuguese Prime Minister Pedro Passos Coelho on Thursday evening urged the pilots to "review their position", adding that the strike could "put the company in danger".
TAP management estimates the strike could cost the airline 70 million euros ($78 million) while the prime minister said on Wednesday it could have a "significant impact on the national economy".
The country's centre right government is putting 66 percent of the company up for sale between now and the end of June.
An earlier attempt at privatisation failed in December 2012.