Will my flight booking API tell me if the airline changes a flight time after my customer has booked?

Yes, in most cases you can see a flight time change through your flight booking API, but how quickly you learn about it and how clearly it is flagged depends on the airline and on the supplier the booking was made with.

The way it normally works is that your API has a retrieve booking request that returns the current itinerary as the airline holds it right now. If the airline has moved a departure, changed an aircraft or cancelled a leg, those new details come back in that response, and you can compare them against what you originally sold. Some suppliers go further and send change messages or notifications into your account so the booking is brought to your attention without you having to look. Others are quieter and expect you to check the booking yourself, which is why many agencies build a habit of re-checking anything departing in the next few days.

Be aware of the limits here. Very small time shifts are sometimes not announced at all, while cancellations and big changes almost always come through properly. Low cost carriers often write straight to the passenger, so your customer may hear before you do if the contact details on the booking are theirs rather than yours. Whether you can accept the new times, move the passenger to another flight or request a refund through the API, instead of contacting the airline, also varies by carrier and by what your plan includes.

The useful next step is to ask us which of your connected airlines and suppliers actually push change notifications, so you know which bookings need manual checking and which will tell you on their own.