Celebrity promises to assist you to the best of their ability to get you to your cruise ship.
The rules have changed since Covid. X does not guarantee you will get to your Cruise. If the airlines cancel a flight onward travel MIGHT be covered if the airlines fault. If weather related you are likely out of luck.
Celebrity does not operate airplanes and cannot control airline schedules, cancellations or delays.
The benefits of scheduling with Celebrity Air are; you don't pay for air till final cruise payment, if you miss your cruise they will try to get you to the ship and if that is not reasonably possible refund your cruise payment.