The first four-day strike by workers employed by SPdH/Menzies – formerly Groundforce – took place last month over 25-28 July followed by a second over 8-11 August. The action has been called by Portugal’s Sima union and transport union ST.

Further walkouts are planned for 15-18 August, 22-25 August and 29 August to 1 September. The action relates to a dispute over pay, including rates for night shifts, and access to parking.

The strikes will affect Portugal’s three main airports in Lisbon, Porto and Faro, as well as island airports in Funchal (Madeira) and Ponta Delgada (Azores). Menzies is understood to employ around 3,500 workers, around 2,000 of whom work at Lisbon airport, where the greatest disruption is expected.

Azorean airline Sata said: "Due to the strike called by Menzies Portugal unions at Portuguese airports, Azores Airlines’ operations to/from mainland Portugal may be affected from: August 8 to 11; August 15 to 18; August 22 to 25; and August 29 to September 1."

The Foreign Office updated its travel advice for Portugal last month. "Industrial action by baggage handlers at Portuguese airports from Friday to Monday during the months of July and August may cause delays," reads the new advice.

"If you are travelling over this period, check for announcements and follow the advice of your airline or tour operator."