that the airline's large hub networks made it ideal for the alliance, and made up for its deficiencies. On 28 August, China Southern Airlines, the largest carrier in the People's Republic of China, signed a preliminary agreement in Guangzhou in its bid to become a full member. In the presence of a number of Chinese and airline officials, Yan Zhiqing, the chairman of China Southern Airlines, said, "This agreement-signing event is an important step forward into the future for China Southern Airlines to adapt itself to the need of further reforms and opening to the international community, as it will strengthen the airline's international cooperation and global competitiveness." On 13 September, Continental Airlines, KLM and Northwest Airlines joined the alliance. Their simultaneous entry was the largest expansion event in airline alliance history. As a result of the three new members, SkyTeam surpassed Oneworld to become the second largest airline alliance, serving more than 341 million customers with 14,320 daily flights to 658 destinations in 130 countries. 2005–2006 Even though member CSA Czech Airlines pledged to help Malév Hungarian Airlines become an associate member of the alliance (as opposed to a full member, an associate has no voting rights), Malév Hungarian Airlines opted to join the Oneworld airline alliance, signing a Memorandum of Understanding late in May. A few days later, SkyTeam announced four new associate members due to join by 2006, each one being "sponsored" by an existing member: Madrid-based Air Europa (sponsored by Air France), Panama-based Copa Airlines (sponsored and partly owned by Continental Airlines), Kenya Airways (sponsored and partly owned by KLM) and Romania's TAROM (sponsored by Alitalia). Every associate adopted a frequent-flyer program of a full member: Copa Airlines already used Continental OnePass; Kenya Airways and Air Europa used Air France–KLM Flying Blue. Following a 23-month joining process since , Aeroflot joined on 14 April 2006. It was the first Russian airline to be associated with any airline alliance. Aeroflot has increased its operational standards, passing International Air Transport Association's (IATA) Operational Safety Audit (IOSA). Delta's subsidiary Song continued to operate as Delta Air Lines. In June, it was announced that Portugália would become the alliance's next associate member candidate. However, in November, rival airline and Star Alliance member TAP Air Portugal, purchased 99.81% of the airline, bringing a sudden end to its candidacy. 2007: Expansion On 4 September 2007, Air Europa and Copa Airlines, and Kenya