The steepest decline came in April, while a slight recovery during the summer stalled in the autumn and winter when new lockdown measures were put in place across the globe due to new virus variants.
With Covid lockdowns persisting across the globe, carriers are looking for ways to preserve cash and bolster liquidity while flights remain impractical.
BA has raised total liquidity by £2.45bn through its pension deferments and final approval on its loan.
The carrier will defer £37.5m in monthly contributions due between last October and September this year after a striking a deal with the trustee of its New Airways Pension Scheme. Under the agreement, BA will also suspend dividend payments to parent IAG until the end of 2023.