Pilots for Dutch flag carrier KLM are threatening to strike over pay and work pressure, according to a letter from the pilots union VNV to its members, the Telegraaf reported on Monday

It remains unclear when any industrial action would be taken, but the paper said none is planned before Friday. KLM and the pilots union VNV reached tentative agreement over a new pay-and-conditions contract for the pilots in May.

However the 2,200 pilots employed by KLM are unhappy about the terms. KLM said the negotiations with the pilots are now in ‘a difficult phase’.

‘KLM does not realise how broad the unrest is and that severe measures are needed to alleviate pressure at work,’ the letter said. ‘ If KLM does not agree with our proposal, then we will begin with work stoppages, the VNV said.

KLM has admitted it is taking the Friday ultimatum seriously, the Telegraaf said.

Dutch pilots working for Irish budget airline Ryanair went on strike last Friday.  There was little disruption to Ryanair flights from Eindhoven, but the strike did upset plans of about 55,000 holiday makers.