LONDON — The parent company of British Airways and Iberia says it lost $8.3 billion last year as the pandemic caused a near-total collapse in international air traffic. IAG’s after-tax loss compared with a profit of 1.7 billion euros the year before. Its revenue slumped 70% to 7.8 billion euros. The company on Friday also backed calls for digital health certificates to be issued to people who have been vaccinated against the new coronavirus as a way to help get passengers back on planes in a safe way.