South African Airways workers on Friday embarked on an indefinite strike for higher wages and against the national carrier's overhaul plan, forcing the cash-strapped airline to ground hundreds of flights.

The stoppage has forced South Africa's largest carrier to cancel more than 300 domestic and regional flights between Friday and Monday.

The company has asked travellers who had flights booked not to turn up at airports and offered them a chance to rebook for free or to fly on other flights operated by partner airlines.

It however said it was making plans to resume international flights by Sunday night.

"The airline is pleased to announce that it is aiming to operate all international flights with effect from Sunday 17 November 2019 and customers should report to the airport as normal," it said in a statement.

More than 3,000 workers, including cabin crew, check-in, ticket sales, technical and ground staff are taking part in the open-ended, according to unions.

Hundreds of placard-waving workers picketed outside the SAA head office near O.R. Tambo International Airport in Johannesburg - one of the continent's busiest airport - singing and dancing.

"We will continue with the strike (until demands are met)," Sifiso Mabena, an aircraft mechanic at the airport told AFP.

Unions pressed on with the walkout after talks with management deadlocked.

Zazi Nsibanyoni-Mugambi, president of the South African Cabin Crew Association (SACCA), however said a new round of mediated talks with the airline was expected on Saturday.

"We have always and will always be willing to negotiate and talk to management, we have told them this time and time again," Nsibanyoni-Mugambi told AFP.

More than 300 flights were cancelled
More than 300 flights were cancelled AFP / Michele Spatari

"We are hoping these talks will bear fruit," said Phakamile Hlubi-Majola, spokeswoman of the National Union of Metalworkers of South Africa (NUMSA) said to eNCA television network.

The airline, which employs more than 5,000 workers, is one of the biggest in Africa, with a fleet of more than 50 aircrafts providing dozens of domestic, regional and international flights each day.

But the company is deep in debt, despite several government bailouts, and has not recorded a profit since 2011.

The unions are pressing for a three-year guarantee of job security and an eight percent across-the-board wage hike. The airline is offering a 5.9 percent increase.

The airline has said it is embarking on a restructuring process that could lead to the loss of close to 1,000 jobs.

The unions have said "inflated contracts" outsourcing work were "crippling SAA's finances (and) literally bleeding SAA dry every day".

The airline has warned that the strike could push the airline to the brink of collapse.

"If the strike continues on a sustained basis we are going to face the prospect of the company having to fold," SAA spokesman Tlali Tlali told eNCA television network .

Finance Minister Tito Mboweni announced in February that the government would reimburse the company's 9.2-billion-rand ($620-million) debt over the next three years.

South Africa is struggling to get its state-owned companies back on track after nine years of corruption and mismanagement under former president Jacob Zuma.