If you are new to cruising, you may not have recognized the merits of @NMTraveller's earlier suggestion to use "Flights by Celebrity". If you book your flights with FBC, you have the option of not paying for the air fare until your final payment for the cruise is due. There is no deposit required either. That is probably the biggest advantage of using them. Until you make this delayed airfare payment, you can also (without penalty) decide to cancel your flight reservation with them and book independently if you wish.
Also, I believe (but am not 100.000% sure) that if your cruise is cancelled by Celebrity after final cruise payment deadline (which means you would have paid for your air fare payment by then), you will get your air fare back, too.