47,462 flights flew between Mumbai and Delhi last year. Bengaluru-Delhi and Bengaluru-Mumbai are the other Indian domestic routes that were on the list.
Three domestic sectors in India are among the top 20 busiest domestic air routes around the world.
The Mumbai-Delhi sector was the third-busiest domestic air route in 2017, according to data published by UK-based OAG Aviation Worldwide. There were a total of 47,462 flights on the sector last year, as per the report published by the air travel intelligence company.
At 64,991 flights, the busiest domestic air route in 2017 around the world was between South Korean island Jeju and the country's capital Seoul. This sector overtook Australia's Melbourne-Sydney route, which recorded 54,519 flights.
The other two Indian domestic routes that found a place on OAG's Top 20 Busiest Domestic routes list are Bengaluru-Delhi, ranked 11 on the list with 29,427 flights, and the Bengaluru-Mumbai route, ranked at 16 with 23,857 flights.
European airlines were missing from the list.
But in terms of punctuality, the Mumbai-Delhi route had a low score of 59.14 percent. The Jeju-Seoul Gimpo and Melbourne-Sydney routes recorded an average one-time performance (OTP) of 74.06 percent and 74.10 percent, respectively.
The Tokyo-Osaka sector topped other routes in terms of punctuality. The route recorded an average OTP of 90.40 percent, the highest on the list.
OAG Aviation also collated data on the world's busiest international air routes in 2017. The Hong Kong-Taipei route was the busiest international air route last year overtaking important sectors such as London- New York and Bangkok-Singapore. 29,494 flights flew between Hong Kong and Taipei last year, with an average OTP of 70.92 percent.The Kuala Lumpur-Singapore sector was the second busiest international air route last year and recorded an average OTP of 78.52 percent.