I have noticed in our trips that it is only PAL (Philippines Airlines) which is systematic when it comes to boarding. A ground crew will be calling the group by the seat number starting from the last then down to the first such as rows 80 to 60 followed by 59 to 40 and so on. This method prevents the overcrowding in the line that a passenger in a low numbered row would just clog the aisle of the plane. Imagine a passenger in row 1 being first to board then all the rest will be waiting for that passenger to sit down. And what if he has several hand-carry baggage he will store in the overhead bin?