A pilot has resigned from South African Airways (SAA) after flying with a fake license for over 20 years.
SAA said it has discovered that William Chandler's paperwork was forged after a "reportable incident" during a flight from South Africa to Germany.
The airline has filed a lawsuit demanding Chandler "million rand".
A security officer of the SAA was also suspended for allegedly attempting to cover up the fake.
The South African newspaper Mail & Guardian (M & G) reported that Mr. Chandler had worked as a flight engineer at the state SAA before getting a job as a pilot in 1994.
He was a senior first officer, a position in which he was a surveillance pilot but did not command a plane.
Sources told the M & G, however, that he had control of an aircraft that "made strange turns" after experiencing turbulence in the Swiss Alps.
SAA stated in a statement that after investigating the incident, he found out that Chandler had only a commercial pilot's license. He resigned later.
Airlines require pilots to hold an international long-haul ATPL.
For an ATPL, pilots must pass several technical and medical examinations and complete 1,500 flight hours.
Licensees must "update" their badges each year in a series of tests that include flight simulations and physical exams.
The certificates are issued in South Africa by the Civil Aviation Authority (SACAA) of the country.
"It seems like the pilot took out what we had issued to him … and changed those documents to give the impression that they have an ATPL," said Phindiwe Gwembu, a spokesperson for the SACAA.
Mr. Chandler had reportedly refused a promotion to captain, forcing him to resubmit his ATPL certificate.
Tlali Tlali, a spokesman for SAA, said the alleged fraud was "disquieting" but did not pose a "security risk" as Chandler still had a flying license and safety training.
Mr Tlali added that "necessary steps must be taken to recover the unduly paid money", including salary, overtime and allowances.
SACAA said it was investigating "loopholes" in its practices.
In a statement, the SAA also stated that it had submitted the license of all SACAA pilots for evaluation and would now receive licenses from audit authorities rather than individuals.
The airline, one of the largest in Africa, has lost money every year since 2011 and lives on government support.
Last November, South Africa's Finance Minister Tito Mboweni said a US investor conference that the company should be closed. President Cyril Ramaphosa, however, has committed to reviving him.