A lot of the time it is not the airline's fault when it comes to PMI, Ground handing for aircraft is a very slow process and then airlines miss there slots and they have to wait until there is one available.
Over the last few weeks it has taken up to 3 hours to turn around an A320 which should be done within an hour. Not monarch a different airline.
Ryanair have turn around times as long as 65 minutes for there aircraft.