The French civil aviation authority has ordered airlines to cancel 70 percent of flights at Paris Orly airport on Saturday and Sunday because of a strike by air traffic controllers.

The cancellations will affect commercial flights  from 0400 GMT Saturday through to late Sunday, the DGAC authority said.

The strike comes as France's second busiest airport prepares for a massive influx for the Paris Olympics, that start July 26. It is the second major air traffic controllers strike in a month. The last one caused the cancellation of thousands of flights across Europe.

That dispute ended with an accord between airport authorities and the main union, the SNCTA. But the second biggest labour group, UNSA-ICNA, ordered the latest stoggage saying that staffing levels were inadequate.

"The managers at Orly continue their penny-pinching and shopkeeper accounts which will quickly lead to our teams being understaffed" by 2027, it said in a statement.

The government condemned the strike.

"I deplore the behavior of some local level agents who refuse to recognise the legitimacy of a majority accord and are making passengers pay the price," deputy transport minister Patrice Vergriete told AFP.

Orly, south of Paris, is the capital's second-biggest airport after Roissy Charles-de-Gaulle and last year carried more than 32 million passengers.

It is a hub for national carrier Air France and the home base for its low-cost subsidiary Transavia. More than 20 other airlines, including easyJet, Iberia and TAP, fly out of Orly.

Only flights between Orly and French overseas territories would operate normally this weekend, the DGAC said.