Chicago O’Hare International Airport moved up the ranks to become the world’s second most connected airport in 2018 but failed to knock perennial winner London Heathrow from the top spot. The annual Megahubs International Index by route expert OAG ranks Heathrow, O’Hare, Frankfurt, Amsterdam Schiphol and Toronto Pearson as the airports with the best connectivity in 2018. OAG’s connectivity index looks at all possible international connections that can be made by passengers in a six-hour window and expresses it as a ratio of the number of destinations served. For Heathrow, passengers could have made one of a possible 66,000 connections on the busiest day. Chicago moved up the top 50 list from fourth to second with fellow US airports Los Angeles and Atlanta coming in at sixth and seventh. Singapore’s Changi, Charles de Gaulle in Paris and Indonesia’s Jakarta Soekarno-Hatta rounded out the top 10. New additions to the top 50 list were airports in Philadephia, Fort Lauderdale, Ho Chi Minh City and Barcelona. “Thirteen US airports make it into the top 50 International Megahubs, illustrating the continued success of the US airline network strategy for connecting passengers,’’ OAG’s John Grant said in a blog post. “China, meanwhile, has three airports in the top 50, along with Hong Kong (SAR). While Beijing Capital Airport is the largest airport in the world for scheduled capacity, it ranks 32^nd  behind Shanghai Pudong Airport and Guangzhou Airport in the connectivity index as it has a fraction of the possible international connections.” The biggest megahubs in the Asia-Pacific were in South-East Asia, with Singapore, Jakarta, Kuala Lumpur, Hong Kong and Bangkok all making it into the global top 15. READ: Cathay's spelling mistake ignites twitter humor. Another Asian hub, Seoul’s Incheon, ranked 15^th. Latin America’s most connected airport was in Mexico City followed by Sao Paulo’s Guarulhos airport. In the Middle East, Turkey's Istanbul, with 55,000 possible international connections in a six-hour window,  edged out Dubai. Kuala Lumpur, home of AirAsia, easily topped the list of the list of low-cost international megahubs. It was followed by airports at Jakarta, Singapore, the Philippines and Thailand. Manila airport jumped from 12^th place last year to fourth place in the latest rankings. Barcelona was the highest ranking European LCC airport in the eighth spot while Fort Lauderdale led the US at ninth thanks to JetBlue. A new feature of the index was the name of the dominant airline in each hub and the share of flights operated by that carrier. "Unsurprisingly for hub airports, 7 of the top 10 Megahubs have a single dominant carrier which operates half or more of all airline operations,'' Grant said. "Los Angeles, Singapore and Jakarta, however, each have a dominant carrier which operates just 20-30 percent of flights, demonstrating that successful hub airports need not be dependent on a single hub-focused airline."