OTTAWA—Airlines say a slew of questions remain about the federal government’s decision to require passengers returning to Canada to show negative results on COVID-19 tests taken abroad. Transport Minister Marc Garneau announced Thursday that air travellers overseas will have to present proof of a negative molecular test—known as a PCR test, conducted with a nasal swab—that was taken within 72 hours of departure, unless the testing is unavailable in that country. National Airlines Council of Canada chief executive Mike McNaney says the Transport Department has yet to provide a list of foreign agencies whose tests are considered acceptable or to establish how airline employees should determine whether a test document is valid. He says the new rule, which mandates a 14-day quarantine in Canada regardless of the test result, will cause “confusion” and “frustration” for carriers and passengers alike. Air Transat vice-president Christophe Hennebelle says Ottawa announced the requirement, which …