Tokyo’s Haneda has kept its top spot for five straight months to July among the world’s busiest airports for on-time departure performance, according to a report released by the U.S. website FlightStats.com providing global flight and airport information.

The latest report, which surveyed on-time departure performance for domestic and international flights at 35 airports in North America, Europe, Asia and other regions, says that 91 to 95 percent of flights from Haneda took off on time between March and July.

In July’s ranking, China’s Beijing airport was ranked worst, with 17.8 percent of flights on time.

Beijing had the world’s second-highest number of travelers, at 81.9 million, last year, according to the Airports Council International. Aviation officials said some flights were unable to take off due to low visibility caused by air pollution from PM2.5 microparticles in addition to congested airspace.

Haneda had 66.8 million travelers, the fourth-largest in the world, with Japan Airlines and All Nippon Airways handling most of the flights.

According to the transport ministry, an airplane takes off from each of Haneda’s four runways every two minutes during daylight. An airport official said fog and other unfavorable weather conditions rarely affect takeoffs.

The number of arrival and departure slots at the airport will be increased from 60,000 to 90,000 by next March.