This will depend on the country of departure of the ticket.
On the Enter billing information page where the credit card details are entered, if the "Cardholder name" can be typed in, you would be able to pay for the booking even if you are not travelling. If the "Cardholder name" appears in a drop-down menu and cannot be changed, you would unfortunately not be able to pay for the booking unless you are travelling.
In some countries, for security reasons, the holder of the credit card used to book a ticket or group of tickets must be one of the travellers on that itinerary, and will be required to show the actual credit card at the airport check-in counter prior to receiving boarding passes.
Skywards members may make a redemption booking for friends and family, and pay for the applicable taxes online with their own credit cards, if the country of departure offers credit card payment.
Business Rewards administrators may also pay for their organizations members bookings by credit card, if the country of departure offers credit card payment.