Travelers are all too familiar with the problem of airlines misplacing their luggage. But it's less common for carriers to lose track of large numbers of actual passengers.

That's the headache facing Pakistan International Airlines (PIA), the country's flag carrier, as it wrestles with a crippling strike by workers who are furious over privatization plans.

"We have no data available on how many and where passengers with confirmed PIA tickets are waiting, because the entire system is shut, servers are down and no booking is being done," a senior official at the company said Friday.

Pakistan's biggest airline said Friday that it has information on around 2,500 passengers stuck in Europe and North America, but many more are believed to be unaccounted for. On a normal day, the airline carries at least 10,000 passengers on local and international flights.

After canceling all flights since Monday, PIA has been scrambling to work with other carriers in Pakistan and around the world to track down and help out its stranded passengers.

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The company said it has arranged with Saudi Airlines for four Boeing 747 jets to fly back around 2,000 stranded pilgrims from the city of Jeddah. It's also negotiating with Etihad Airways and Turkish Airlines to help passengers trying to get to and from Europe and North America.

Bookings have dropped as news of the paralyzing crisis has spread, PIA said.

Labor unions have been demanding that the government roll back efforts to partially privatize the loss-making carrier, which has been relying on public subsidies to keep operating.

Security forces used water cannons and tear gas on protesting PIA workers in the city of Karachi on Monday after the government tried to invoke a decades-old law to stop them from going on strike. Two airline employees were killed in the violence, deepening the anger.