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An interactive map of the world’s best and worst airports for flight delays

Green: More than 75 percent of flights leave on time. Yellow: Between 60 and 75 percent leave on time. Red: Fewer than 60 percent leave on time.

The world's most reliable major airports are in Japan and its least reliable are in China, according to a new study on flight departure times by the company FlightStats. The report looked at dozens of the world's highest-traffic airports, examining thousands of flights from each during the month of June to see how frequently they left on time. The more likely a flight from that airport was to leave on time, the better the airport could be said to perform.

I've mapped out a selection of the data above. The map is interactive: You can zoom in and out as well as use your cursor to highlight airports to see how many of their departing flights left on time this June. The airports marked in green had more than 75 percent of their flights leave on time. The airports in yellow had between 60 and 75 percent of flights depart on time. The airports in red scored below 60 percent – in some cases way, way below.

First, some caveats: The data include  thousands of flights per airport, but the limited time frame means that results can be skewed by weather. And FlightStats concedes as much, pointing out that some unusual weather in North America may have created more delays than usual. And Hong Kong's not-great performance, with 63.66 percent of flights leaving on time, does not appear to represent the norm: the airport reported a substantially better 77 percent in January. Finally, the report focuses heavily on Europe, North America and East Asia. While it's true that most of the big airports are there, not all of them are. I'm not sure why they don't report data for Bangkok, Dubai or Jakarta airports, which are among the world's busiest.

The two best performing airports were both in Tokyo: Flights out of Haneda and Narita had, respectively, a 95.04 and 86.38 chance of leaving on time. No other airport was even close to Tokyo Haneda. A chart of the top 10 performers is posted below.

The two worst performing airports were also in East Asia, but in China: Beijing and Shanghai. Only 28.72 percent of Shanghai flights left on time. In Beijing, it was only 18.3 percent, the lowest in the world. By comparison, 42 percent of flights out of Beijing leave more than 45 minutes late. That's almost half. Other high-traffic Chinese airports, of which there are many, also scored poorly.

Why are flights out of China's airports so late so frequently? It has to do, according to the Wall Street Journal's Te-Ping Chen, with air traffic control, the Chinese military's still-tight control over airspace and, as is often the case in China, a lack of transparency:

Aviation experts cite military control of China’s skies as one difficulty for civil aviation. Former Hong Kong Dragon Airlines flight attendant Clare Fung, who teaches at Hong Kong’s Polytechnic University, said the airport woes are largely the result of poor air-traffic control. Another issue, she said, is that unlike U.S. airports or, say, London’s Heathrow, China’s airports are largely government-controlled. “It’s difficult to improve, to be honest, because the industry is not so commercially oriented,” Ms. Fung said.
That fact can make the reason behind delays less transparent, she said. “When I was flying, we’d always encounter severe delays flying through China, but they’d never tell you the real reason,” she said.

Some European airports also reported high rates of delays. Istanbul and Moscow are two of the only other airports where a flight had a less than 50 percent chance of leaving on time. Rome and Paris, despite being in wealthy European capitals but maybe because of all the tourist traffic, scored just under 60 percent on-time departures.

A number of European airports, particularly in Germany and Scandinavia (but also in Spain, believe it or not), seem to score well by on-time performance. Airports in the United States generally do pretty well on average, although the big East Coast airports appear a little more strained. Three American airports are on the top 10 performers list: Seattle, Minneapolis and Phoenix. But it's worth noting that those are all medium-sized airports; the bigger American airports don't do as well. New York's have about a two-in-three chance of having a flight leave on time.

One interesting case is New Delhi's Indira Gandhi International. It's big, moving about as much traffic as Newark or London Gatwick, but managed a higher on-time score than both: an impressive 84.28 percent. Only 1 percent of New Delhi departures were cancelled. India is often described as having poor infrastructure compared to the West, while China's infrastructure is often praised as a big success story. Broadly speaking, that might be true, but Indira Gandhi International is a nice counterfactual, proof that sometimes Indian infrastructure can outperform much of the world's.