No airline I've ever booked an international flight with has required passport information to accept the booking.
Certainly you have to fill in the APIS section of your booking (Advance Passenger Information Service) at some stage before you try to check in, and that includes your passport number, but it's not a prerequisite to buying the ticket.
Edited: 4 years agoUse your old passport number (if necessary) and then just update the details when your new one arrives.
My wife did this only in December for a business trip she is on now.
It's any visas that you may require which will need the new passport details.
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