Line No.5 line (purple) may be extended north to Tan Son Nhat Airport.
Ho Chi Minh City is seeking permission to expand one of its metro lines to Tan Son Nhat, now the country's biggest airport.
In a proposal submitted to the Ministry of Planning and Investment on Tuesday, the city recommended a two-kilometer line linking the airport and to the planned Metro Line No.5 in Tan Binh District.
It asked the ministry to seek funding from the Export-Import Bank of Korea for the project's feasibility study, expected to be started next year.
Line No.5 will start at the Saigon Bridge and end at Can Giuoc Bus Station in Binh Chanh District.
The city's authorities have managed to secure funding for its first stage, estimated at US$1.75 billion. Nearly 30 percent of the cost will be covered by the state budget.
Work on the line's first stage will not start until the project is approved by legislators, Bui Khac Huynh, deputy chief of the management board for HCMC's urban railways, told the press in April.
Under Vietnam's law on public investment, any project which costs the state budget more than VND10 trillion ($457.87 million) must get approval from the National Assembly, the country's legislative body.
So far, the city has launched construction of the first two of its six metro lines, both expected to start operating in 2020.
The first line runs between Ben Thanh and Suoi Tien in District 9 started in December 2013, while the second one connects An Suong and the new urban area Thu Thiem in District 2.