To Cathay Pacific change flight booking, start by visiting the official Cathay Pacific website or app. Log in to your account and navigate to the "Manage Booking" section. Enter your booking reference and last name to access your reservation details. Select the flight you want to modify and choose the "Change Flight" option. Follow the prompts to make changes to dates, destinations, or passenger information. Review the modifications and confirm the updates to your booking. After confirmation, you'll receive a revised itinerary via email. For any assistance, Cathay Pacific's customer service at 1-818-878-8939 is available to help.