Crew sickness in Rome caused an aircraft to become stuck there for several hours awaiting a new crewmember to be flown out. Quickest way to get passengers to Belfast was to bus them to Manchester and fly from there. Aircraft then flew 328 as normal if a little late before flying empty back to Manchester.
Other airlines would have cancelled completely, I think Jet2 generally do a good job of making sure people get where they need to be, better late than never.