Chicago O'Hare offers more flight connectivity than any airport in the U.S., according to the Megahubs U.S. Index prepared by airline analytics company OAG. 

O'Hare took the top spot by offering as many as 81,913 possible one-stop domestic flight connections during a three-hour window. 

It's the third consecutive year that O'Hare has held the top U.S. position in the OAG Megahubs Index. The airport is buoyed by Chicago's central U.S. location and the hub operations of United and American. Both carriers have pursued a strategy of beefing up regional connectivity from O'Hare over the past year. 

Rounding out OAG's top five for domestic U.S connectivity are Delta hub Atlanta, American hub Charlotte, American hub Dallas/Fort Worth and Denver, which is a United hub and one of Southwest's largest focus cities. 

The biggest mover in the 25-deep ranking was New York LaGuardia, which rose from 24th to 14th. Philadelphia was another significant mover, jumping from 14th place to 10th place. Honolulu was the only airport to drop out of the top 10, sliding from ninth in last year's index to 15th this year. 

OAG also does an international ranking for flight connectivity. London Heathrow topped the international ranking, followed O'Hare, Frankfurt and Amsterdam. 

"Megahubs are incredibly important for the global travel ecosystem," senior OAG analyst John Grant said in a statement. "They increase efficiency, competition and choice, and, most importantly, create a boundary-less world for travelers."

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