Actually, it works out a little better than in my previous post.

Because they say in the T&Cs that "Additional XP will be rounded up to the nearest whole number", and because so many of the XP values are not whole numbers when increased by 20%, 9 of the entries in the 16-entry XP earning table are rounded upwards.

Here is the XP earning table, with the values increased by 20% shown in red. For those that are not whole numbers, I have rounded these up to the nearest whole number, shown in green.

Domestic Economy flights end up with a 50% earning bonus - 2XP goes to 3XP (rather than to 2.4 XP) - with smaller additional bonuses above the nominal 20% for the other green figures