You can easily add an upgrade to your booking in advance by paying a supplement. Depending on availability, you may still be able to upgrade during online check-in, at the airport or once on board.
The system automatically checks which of your flights are eligible for an upgrade. Click the “Upgrade” link in your booking, confirm your selection for the flight or flights on which you want an upgrade, and then enter your payment details. You will receive a booking confirmation to the email address you provided.