You can fly an aeroplane full and still lose plenty of dough.
The number one cost remains fuel. If you're charging the same for tickets as your competitors - which you need to do to fill the aeroplanes - but are flying aeroplanes that burn 30% more per ASK (744 vs. 77W) you're going to lose.
That's the real reason international continues to burn money...literally.
Management book the bonuses for the failures of 10 years ago and staff are left to pay the price.