“We must continue to keep up the pressure for our wage demands,” the unions said in a statement, arguing that their objectives were to “sign an agreement that is reasonable for everyone”.
The announcement of new strikes, after 11 previous days of strikes, called by unions representing employees from pilots and cabin crew to ground staff, comes ahead of an airline consultation on the management's salary proposals.
The new dates are May 3rd, 4th, 7th and 8th.
The embattled CEO of Air France-KLM, Jean-Marc Janaillac, last week threatened to resign if Air France staff continued to reject his wage proposals.
Staff and management at the French carrier have been locked in a dispute over pay since February.
Unions say workers deserve to benefit from years of belt-tightening that have returned the carrier to operating profitability, after seeing their wages effectively frozen since 2011.
Management says it cannot afford their demands of a 5.1 percent increase this year, saying it would undo the benefits of the restructuring efforts.
It is offering an increase of two percent for 2018, with another five percent staggered between 2019 and 2021.
Janaillac said he would circumvent the unions to put the proposals directly to staff in an online ballot.
The strikes have chiefly affected short-haul flights.
The airline says the dispute has set it back by 220 million euros ($272 million).
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