MUMBAI: With around 130 flights between India’s political capital and the commercial capital every day, Mumbai-New Delhi was the third busiest air route in the world last year.A total of 47,462 scheduled airline flights were operated between the two airports in 2017, next only to South Korea’s Seoul Gimpo-Jeju airports (64,991 flights) and Australai’s Melbourne-Sydney aiports (54,519), according to data released by UK’s OAG Aviation Worldwide Ltd, an air travel intelligence company.The ranking is based on total flights operated between two airports and not two cities. Unlike megacities such as New York and London, Mumbai and Delhi have only one major airport each, so all their air traffic is routed from these two airports.While Bengaluru-Delhi was the 12th busiest route in the world with 29,427 flights between the two airports last year, Bengaluru-Mumbai was 19th, with 23,857 flights. But if one were to look at the top 20 busiest domestic routes, Bengaluru-Delhi would take the 11th rank and Bengaluru-Mumbai 16th.In fact, four out of the top five busiest air routes (both international and domestic together) in the world is in the Asia-Pacific region, with Brazil’s Rio De Janeiro-Sao Paulo (5) being the only outsider.Among international routes also, all the top five routes were within Asia and only two non-Asian routes—New York La Guardia-Toronto (6) and Dublin-London Heathrow (9)—in the top 10. Hong Kong-Taipei was the busiest international route in the world last year, with 29,494 flights. If both domestic and international routes are listed together, then Hong Kong-Taipei would be the 11th busiest route in the world.When it comes to punctuality on the 20 busiest domestic routes, Japan emerges on the top with Tokyo Haneda-Osaka route (17th busiest, 21,900 flights) seeing 90.40 % of flights departing and landing within 15 minutes of their scheduled time. Jeju-Seoul, the busiest route, had an average on-time performance (OTP) of 74.06 %.In comparison, the Mumbai-Delhi route recorded an OTP of 59.14 %— among the worst among the 20 busiest air routes. According to OAG, a flight is considered to be on time if it arrives/depart within 14 minutes and 59 seconds (under 15 minutes) of its scheduled time.A senior A320 commander, requesting anonymity, said: “If the other airports that are as busy or busier than Mumbai and Delhi can manage better punctuality, why can’t we better ourselves?’’ On the Melbourne-Sydney route, for instance, airlines recorded an OTP of 74 %. Melbourne airport has a set of cross runways, very much like Mumbai, while Sydney has three runways, which include a set of parallel runways, comparable to the three runways of Delhi. However, Melbourne handles about 10 million less passengers than Mumbai does annually.Among airlines that operate on the Mumbai-Delhi route, SpiceJet recorded best performance with an OTP of 72.3 %, followed by IndiGo (71.7%), Go Air (54.8%), Jet Airways (48.5 %), followed by Air India at 48.4 %. The two major factors that influence OTP are scale and complexity of operations. Airlines such as Jet Airways and Air India that operate both domestic and long-haul international flights run a complex route network, than say, GoAir, IndiGo or SpiceJet which largely operate domestic routes and a few international medium-haul ones.When it comes to the scale of operations, IndiGo was ranked fourth in the OTP list for top 20 mega airlines (biggest in the world in terms of number of scheduled flights operated). But this OTP data takes into account only arrivals and so the role of “schedule padding’’ done by most airlines cannot be ruled out. For instance: a schedule padding has a 1 hour, 50 minute-long flight listed as 2 hour, 20 minute-long flight so that a delay in departure can doesn’t show up as a delay in arrival.