You can buy an extra baggage with a credit card during online check-in 

It is possible to purchase extra baggage online only for flights operated by ITA Airways .

LIGHT FARE INFORMATION 

For hand baggage that exceeds the permitted weight / size or baggage to be checked in the hold, a supplement is payable per way for the first baggage.

• National flights: € 50 if purchased in the 'My Flights' section and online check-in, through the Customer Center and authorized travel agencies; € 65 if purchased at airport ticket offices or check-in counters. The standard baggage allowance applies for additional checked baggage.
  
• International flights (to/from Europe, North Africa and Middle East): €55 if purchased on the ITA Airways website in the section My Flights, during online check-in, or via the Customer Center and partner travel agencies; €65 if purchased at the check-in desks at the airport. For further baggage to be boarded, the standard baggage allowance will apply
  
• intercontinental flights:
  
  • from Europe to Brazil, Argentina and Japan is equal to €65 if purchased via the web or €75 if purchased at the airport;
  • €65 on flights from Europe to the United States, and US $70 on flights from the United States to Europe whether purchased online;€75/US$80 if purchased at ticket offices or airport check-in desks;  
  • from Brazil, Argentina and Japan to Europe is US $65 if purchased online or US$70 if purchased at the airport;
• In the case of onward travel with codeshare flights operated by Air France, KLM and Delta partners, the purchase of baggage is only possible at the airport (ticket offices and airport check-in) where the journey begins. The standard baggage allowance is applied for additional checked baggage;
  
• It is not possible to buy baggage online at the reduced price of € 50, nor through the Contact Center, for flights operated by other carriers or departing from the following airports: Amsterdam, Geneva, Tirana, Zurich.
  
• In case of purchase of the baggage service at the airport, the payment of a supplement defined by the Airport Manager may be required, which varies according to the airport of departure.
  
• The above prices are subject to change in relation to the time of purchase of the baggage service
  
• The fare applies to both return and one-way flights
  

REFUNDS 

You are entitled to a refund of the amount paid for additional baggage in the following cases:

• the flight is not operated by ITA Airways 
• the original flight has been canceled and you have refused the new flight proposed by ITA Airways 
  
• baggage for which you purchased additional baggage in advance is lost and not found within 45 days
  
• sickness / death (in both cases, the waiver for sickness / death must be proven by a valid hospital certificate or death certificate):
  
• of close relatives: spouse, children (including adoptive parents), parents, brothers / sisters, grandparents, grandchildren, in-laws, brothers-in-law, gender and daughter-in-law; in this case it is necessary to demonstrate the degree of kinship with an appropriate certificate (family status or other issued by bodies in charge such as district or registry office)
  
• of passengers, relatives or friends, present on the same PNR
  

You are not entitled to a refund if:

• you decide to bring less baggage than you bought.