A 1Time aircraft forced to do an emergency landing earlier this month after an engine failed, experienced engine difficulties again on Monday, the airline said.
The difficulties were encountered as flight T6 647 from Cape Town started its descent into Durban.
"During cruising altitude of 35 000 feet, cockpit indicators revealed that the left-hand engine had experienced technical problems," it said in a statement.
"Safety will always be 1time's first and foremost priority and we will never compromise our passengers, crew or aircraft," said CEO Blacky Komani.
"We also wish to reiterate to our customers that Boeing considers the MD80 one of the safest aircraft in the skies today, and with our focus of safety and customer service at the top of our agenda, we assure passengers that incidents such as these are considered to be very serious and we will work effortlessly to establish the cause of the problem."
Airline spokesperson Refilwe Masemola later said the aircraft was the same one that had to make an emergency landing at Durban's King Shaka International Airport on 5 August after its left-engine failed.
"This is the same aircraft, but this time it is a different engine. Everything was checked out. This was an unforeseen problem," she said.
The aircraft was able to safely operate on its other engine and no one was injured.
The SA Civil Aviation Authority (SACAA) could not be reached for comment.
Last time, the plane was going to Cape Town, when it had to turn back minutes after take off.
The runway at the airport was closed for the emergency landing.
At the time, SACAA spokesperson Phindiwe Gwebu said debris had fallen out of the left engine.