If an airline changes a flight time after I have already sent the itinerary, does the plan update itself or do I have to redo the whole thing?
In most cases you do not have to redo it. When the flight was booked through a connected supplier, a schedule change usually comes back into the system as a message against that booking, and the itinerary you built on top of it is updated to show the new timing rather than being thrown away. The rest of the plan, the hotels, the transfers, the sightseeing and everything you wrote yourself, stays exactly where it was.
What the system will not do for you is decide what the change means for the trip. If the new arrival time lands after midnight, the airport transfer you arranged and the first night at the hotel may both need to move, and that is a judgement call about your customer, not something software should quietly make on its own. A good builder flags the affected day and leaves the decision with you, so check the days either side of the changed flight rather than only the flight itself.
How quickly the change reaches you depends on the airline and the supplier you booked through. Some send schedule updates promptly and in a form the system can read, others are slower or expect the agent to pick the change up from their own portal. Anything you arranged outside the system, such as a local guide you booked by phone, will never update on its own because nobody has told the system it exists in that form.
When you next get a schedule change, watch how it appears against the booking and how the itinerary you already sent reacts, so you know what your team still has to handle by hand.
