If you travel with a broken limb or in a cast.
Yes but you must produce a medical certificate confirming you are fit to fly.
For your comfort and the comfort of other guests, we recommend you book an extra seat.
To book an extra seat, at the guest details page, please enter your passport details.
Then for the second guest, you should enter “EXTRA” in the first name field and “SEAT” in the Last Name field with the rest of the details to mirror your passport.
Please note that if you purchase an EXTRA SEAT you must “Pick A Seat” to ensure you get both seats side by side. There will be no cabin baggage allowance allocated for the extra seat. – source: FAQ