By Allison Lampert and Inti Landauro (Reuters) -Labour strife in Europe is driving expectations of more travel headaches during the busy summer season, with airports and airlines clamouring to find more workers, minimize cancelled flights and reduce delays for passengers. On Thursday, some 1,000 SAS pilots in Denmark, Norway and Sweden said they could go on strike from late June, even as workers at France’s Charles de Gaulle airport walked off the job, with a quarter of flights cancelled. Airlines, battered by a slump in travel during the pandemic, have been counting on a strong summer, with f…