Online booking is for the convenience of the passenger to sit at home/Office and book their tickets. The purchase amount is debited to the credit card as soon as you complete the booking process and why do they need the Credit card for check in? Is it only because the name of the Passenger name does not tally with the name on the Credit card? Normally there should be an option to confirm if the Passenger and the Credit Card owner is same and if not they should not ask for the original credit card for check in as the ticker fare is already paid.