Two employees of Pakistan International Airlines were killed after a standoff with police on Tuesday, which led the national flag carrier to wind down its operations across the country.
As news of the deaths spread in the evening, the flight operations began shutting down in solidarity with the protestors, officials said.
The operations were suspended around 4.00 p.m. at Lahore, Islamabad, Peshawar and Quetta airports, officials confirmed.
PIA Lahore spokesman Athar Awan said flight operations were halted after two PIA employees were killed in clashes with police and Pakistan Rangers.
A Civil Aviation Authority official in Quetta, on condition of anonymity, told Dawn thatflights to and from Quetta were delayed indefinitely following the protest outside Karachi airport.
Two protestors died after they sustained bullet injuries and five others were injured, but Rangers and police denied "handling protestors violently" and opening fire on them at the site of the clash, Dawn reported.
The incident came a day after Prime Minister Nawaz Sharif enforced the Essential Services Maintenance Act, 1952, for six months in an effort to block the impending strike of the airlinestaff.
The employees of Pakistan International Airlines are opposing the airlines' privatisation and are determined to disrupt flight operations from Tuesday despite the government's threat to terminate their services for work stoppage.
A large contingent of Rangers and police personnel was stationed outside the major airports to control the protestors and avoid any violence.