World's busiest flight routes 2021: Sydney-Melbourne route back among world's busiest

A surge in flights between Sydney and Melbourne has seen the route climb back into the world's 10 busiest, data shows.

Flight data analyst OAG ranks the world's busiest routes by the number of seats available. In April, Sydney-Melbourne climbed to number seven on the top 10 list, with 598,779 seats.

As Australia's airlines reduced domestic capacity in the wake of the COVID-19 outbreak and state border closures last year, the Sydney-Melbourne route disappeared from the top 10.

Previously it was the second-busiest route in the world, behind only South Korea's domestic route between Seoul and Jeju island. The latter route remains the world's busiest now, with more than 1.4 million seats for April.

Travel has bounced back in Australia, with Virgin Australia announcing last month plans to lease eight or nine more Boeing 737s in order to increase capacity on domestic routes.

Qantas chief executive Alan Joyce told the CAPA Centre for Aviation this month the airline had seen Australia's domestic market get stronger each quarter and he expected Qantas to be back to 80 per cent of its pre-COVID-19 capacity in the fourth quarter of this financial year.

"Despite the stop and start, people are getting comfortable with what the situation is around borders," he said. "They're travelling. And then each time it looks like when the borders are closed, it's for a shorter period, the rebound is faster."

The Sydney-Melbourne route now has a fourth player in addition to Qantas, Virgin and Jetstar, with regional airline Rex making its first foray into connecting capitals, launching on the route in February.

While the federal government's tourism scheme for half-price flights has also reportedly boosted airfare sales recently, the scheme will not have impacted the Sydney-Melbourne route as it was restricted to selected regional destinations from the capitals.