Ongoing work to upgrade a runway at Soekarno-Hatta International Airport, which serves travellers to and from Jakarta, will be completed only in January 2018.
The upgrading is aimed at reinforcing the airport's North runway to allow wide-body aircraft such as the Boeing 777 to carry a maximum load, said Mr Agus Haryadi, corporate secretary and head of legal affairs of the state-owned airport operator Angkasa Pura II.
The construction, which started last month and will cost about 250 billion rupiah (S$26.5 million), is expected to be completed in about 15 months. "One of the reasons to cut the number of flights is runway maintenance," Mr Agoes Subagyo, a spokesman for the Directorate General for Air Transport, told The Straits Times.
On Monday, Singapore Airlines (SIA) said it was told by the Indonesian authorities to cut existing flights to Jakarta due to runway maintenance works at the airport.
This, just weeks after it announced the cancellation of a new Singapore-Jakarta-Sydney service for the same reasons.
The latest development means the national carrier has to cut five Singapore-Jakarta flights it operates a week, starting on Dec 1.
Affected flights are SQ962 and SQ963 on Mondays, Tuesdays, Wednesdays, Thursdays and Saturdays, said SIA.
Mr Agus said the maintenance work is carried out almost daily from 10pm to 5am and affects 51 flights during that window. He added that those were mostly domestic flights by Garuda Indonesia, Lion Air, Wings Air and Batik Air, some of which were diverted to the South runway. But Garuda and Lion Air said they are not affected by the maintenance works.
A check by The Straits Times showed that while flights SQ962 and SQ963 do not fall inside the 10pm to 5am window, the planned Singapore-Jakarta-Sydney service does.
It is unclear why the Indonesian civil aviation authority had asked SIA to cut these flights.
Aside from SIA, no other airline has issued statements on being affected by the runway maintenance. The Civil Aviation Authority of Singapore (CAAS) said on Monday that it hopes the "runway maintenance works will be completed expeditiously and that the impact on airlines will be fairly distributed".
SIA has been operating 63 flights a week to and from Jakarta since July 2013. It is also the second busiest air route in the world after Hong Kong-Taipei flights.
Some analysts say it is one of the most lucrative routes for SIA as it serves mainly more well-to-do tourists, businessmen and executives who regularly travel between Singapore and Jakarta.
Soekarno-Hatta International Airport operates two parallel runways - North and South - each 3.6km long and 60m wide. There are three terminal buildings at the airport, serving more than 50 domestic and foreign airlines.