Its quite easy really. With Monarch all ZB flights are scheduled and MON flights are charter. With Jet2 all flights are scheduled except those you cannot book flight only.
True but in terms of passengers on these flights, many are still booked on them using the various charter arms of the businesses... Numbers that would once have been travelling on airlines including xl and the Spanish operators we used to see over the summer such as Air Europa, iberworld etc... The passengers are pretty much still there just not all on solely 'charter' flights... so thats why the figures cant always be that trusting.