COPENHAGEN -- Pilots for Scandinavian Airlines on Friday launched an open-ended strike following the collapse of pay negotiations, forcing the company to cancel virtually all its flights -- 673 of them, affecting 72,000 passengers.

The Stockholm-based carrier said talks on a new collective bargaining agreement with the SAS Pilot Group, which represents 95% of the company's pilots in Sweden, Denmark and Norway, collapsed early Friday.

In airports throughout the region, SAS staff in yellow vests were assisting stranded passengers to rebook or obtain refunds.

Mina Kvam Tveteraas and her friend Bettina Svendsen were stranded at Stavanger Airport in Norway after their flight to Copenhagen was cancelled.

"We have booked a hotel for three nights and the rooms are not refunded," Kvam Tveteraas told Norway's TV2 channel. "I have no idea what to do and I'm mad."

The pilots' negotiations that started in March mainly centred on salary increases and working hours.

Details have not been released but the pan-Scandinavian union says it wants salaries to be in line with the market rate, while SAS negotiators have called the requests "unreasonable and extreme." SAS spokeswoman Karin Nyman said the pilots' demands "would have very negative consequences for the company."

Wilhelm Tersmeden, chairman of the Swedish pilots association, said SAS employees are facing "deteriorated working conditions, unpredictability in planning work hours and insecurity for their own job."

"Almost one in four SAS flights is flown by subcontractors and we want to know what our future looks like," he told Sweden's TT news agency.

Jacob Pedersen, an analyst with Denmark's Sydbank, estimated the strike in average would cost between 60 million and 80 million Swedish kronor ($6.3-8.4 million) a day.

The strike "makes it clear that SAS is more vulnerable than we previously expected," he said. "Competition is tough, and with a European economy moving at a slower pace, SAS may also fight harder for profits this year."

The company said the strike doesn't include flights operated by SAS partner airlines, making up approximately 30% of its departures, and is not expected to affect other airlines' departures and arrivals.