Frequent flyer programs are defined by the sale of miles or points to program partners such as hotel chains and car rental companies, co-branded credit cards (co-branding), online malls, retailers, and communication services. The amounts can be significant, such as the disclosures made by the top 5 revenue-producing carriers for 2018: $1,144,803,233 (Qantas Group), $5,571,000,000 (American Airlines), $4,229,000,000 (United Airlines), $3,407,000,000 (Southwest Airlines), and $4,110,000,000 (Delta Air Lines).[20] (2018 carrier results were based upon recent 12-month financial period disclosures.