Drivers staged walkouts over 15-18 April, leaving fuel supplies at the country’s busiest airports – Lisbon, Porto and Faro – so low that a number of flights had to land in Spain en route to refuel for fear they would not be able to in Portugal.

Portuguese prime minister Antonio Costa declared an energy crisis, requiring drivers to guarantee minimum fuel supplies to maintain vital services.

The deadlock was broken after four days when representatives for Portugal’s national union of dangerous goods drivers agreed to resume negotiations.

However, Reuters reports no agreement was reached during a meeting on Monday (29 April), after which the union’s legal advisor Pedro Henriques told reporters it would give employers an extra week to meet drivers’ demands but stressed a new strike was “very likely”.

During the previous strike, easyJet was among the airlines forced to land in Spain to refuel before continuing onwards to Portugal.

Portugal’s national airport operator ANA, meanwhile, warned passengers their journeys could be affected.