DOHA, Nov 10 (Reuters) - High oil prices could delay efforts by airlines to restore balance sheets weakened during the pandemic, the head of a global airline industry body warned on Wednesday. Crude prices have risen 66% so far this year as economies exit lockdown and supplies remain tight. “I think it’s going to be tougher, but I don’t see that airlines can avoid that. They will have to strengthen their balance sheets,” Willie Walsh, director general of the International Air Transport Association, told Reuters. “For some airlines it will take time and a higher oil price probably does slow down the recovery period,” he said. Labour shortages are also a concern and represent a real industry risk for the first time in decades, he added. On the positive side, forward bookings are increasing and stretch up to a year ahead as travel restrictions are lifted. Airlines are likely to add significant numbers of seats after the United States lifted COVID entry restrictions, but strong demand will overcome any concerns about overcapacity, the former head of British Airways owner IAG told Reuters. (Reporting by Alexander Cornwell, Tim Hepher, Editing by Louise Heavens)