The aviation industry is a useful altimeter for the lingering impact of covid-19. Air travel ground almost to a halt in 2020, as virus-induced restrictions kept people at home. Since then it has clawed its way upwards as lockdowns have eased and travellers who had been denied holidays, visits to loved ones and business trips have gradually returned to the air. Capacity, measured by available seats, is set to end 2022 at around 4.7bn,…