Dutch national carrier KLM cancelled dozens of weekend flights Friday at Schiphol airport, hit hard by a strike and staff shortages as it struggles to cope with pre-coronavirus passenger numbers.

The airline axed 47 single and return flights on Saturday and Sunday, after cutting 28 return flights on Friday following an urgent plea by the airport, seen as a major gateway to Europe.

"The cancellations should contribute to Schiphol's request to keep operations at the airport manageable because of staff shortages," KLM said in a statement.

"These cancellations in KLM's flight schedule also contribute to reducing the workload" for its own staff, the airline said.

Schiphol -- Europe's busiest airport in terms of aircraft movements in 2019 when more than 70 million passengers passed through its gates -- saw numbers plunge during the coronavirus pandemic.

But after the Dutch government dropped its last major Covid-19 restrictions in mid-March, passenger numbers once again took off, peaking around the Easter weekend which was still continuing.

The International Air Transport Association (IATA) condemned Schiphol's request to airlines as "outrageous". 

"Passengers book flights weeks or months in advance," IATA told the Dutch news agency ANP. "Some of them will have to cancel their holiday plans."

Dozens of flights were delayed last Saturday after some KLM ground staff walked out in a wildcat strike to protest staff shortages and long working hours.

The strike came on the first day of the May school holidays, with many families going on holiday for the first time since coronavirus restrictions were dropped.

Airlines "have complied with Schiphol's request to allow fewer passengers to travel this weekend because of the crowds", the airport said in a statement.

"The crowds are caused by the May holidays and the personnel shortages in the aviation sector," it said.

The airport said it would have talks with airlines on Sunday to discuss the problem.

Meanwhile, at least one travel company has moved operations to the nearby and less busy Rotterdam The Hague Airport.