South African taxi drivers on Friday blocked roads to Johannesburg’s airport, holding up thousands of travellers in the latest protest against ride-hailing app Uber.

Uber Technologies Inc’s service has triggered protests by taxi drivers from London to Hungary and New Delhi as it upends traditional business models that require professional drivers to pay steep licensing fees to drive cabs.

Hundreds of drivers blocked the main highway to Africa’s busiest airport, O.R. Tambo International, causing long traffic jams on Friday.

“Uber is illegal,” Reuben Mzayiya, a spokesman for the metered taxi business in Gauteng province, told broadcaster 702 Talk Radio.

“If you want to operate, you must register with the department of transport and fulfil all the requirements. Uber doesn’t do all those things.”

He added, “It just operates a parallel structure with a fraction of what we are charging.”

The protests have prompted the South African imports operator, ACSA, to begin talks with airlines about possiblee flight delays, spokeswoman Refentse Shinners said.

“We are currently negotiating with our airline partners to see how we can accommodate them,” Shinners said. “We cannot as yet make any guarantees in terms of those arrangements.”

Uber has attracted more than 500,000 users and 4,000 drivers across South Africa since its 2013 launch.

(Reporting by Tiisetso Motsoeneng; Editing by Clarence Fernandez)