Air travel across Pakistan has been badly disrupted by a strike against plans to privatise the national carrier Pakistan International Airlines.
PIA said none of its scheduled flights took off from anywhere in the country.
Staff stepped up their industrial action after two employees were shot dead during clashes with security forces in Karachi on Tuesday.
The strikers have been threatened with the sack if they hinder efforts to reform the loss-making airline.
Prime Minister Nawaz Sharif has said they may even be imprisoned.