I have an Alitalia flight from Munich, Germany to Delhi, India and I booked it using an online agency. I did not use my credit card for the booking and paid using my friend's credit card. Do I still need to carry the copy of the credit card and the authorization letter to the airport even when I booked the flight from a third party? I cannot find the information on the Alitalia website.
The Alitalia website clearly states that:
Attention: in order to ensure protection against frauds, you might be asked, by authorized personnel, to show the credit card with which the ticket was purchased. Failure to exhibit the credit card, in original or in copy (if you are not the holder of the card with which the ticket was purchased), could result in not being allowed onboard.
So in case, the purchase was from their website you are supposed to carry the card or a copy + authorization letter. Since you made a purchase using an online agency, this may not be required unless the agency communicates the method of payment or card requirement to the airline (which rarely happens).
I would suggest that to be on the safe side make a copy of the card blocking all of the card number digits except the last four and get an authorization letter. The letter can be handwritten, typed, scanned etc as long as it is signed.