The world needs about twice as many commercial airline pilots as it has, which means pilots in emerging markets such as South Africa could quadruple their salaries.

They’re are leaving for better paying jobs, and attrition is up to five times more than the usual rate at South African Airways.

The average pay for a commercial airline pilot in South Africa is about $50,000, according to Payscale. In the U.S., the same job pays a $63,738.

In the last year, 60 South African Airways pilots left for jobs with foreign airlines — mainly in the Middle East, according to to SAA Pilots Association Chairman Captain Jimmy Conroy, Times Live reported.

Salaries paid to South African Airways pilots are “exorbitant and unaffordable,” SAA Board Chairwoman Dudu Miyeni said in 2015, according to Times Live.

“SAA has a normal attrition rate of 15 -to-25 pilots per year. Recent negative publicity together with hostility from certain quarters has caused some pilots at SAA to re-evaluate their career options‚” Conroy said in a statement.

South African Airways isn’t unique for high turnover of pilots.

Most airlines have a very high turnover rate and pilots can demand a lot more money when they’re being head hunted by bigger airlines, according to JobMail.

Chinese air traffic could almost quadruple in the next 20 years, making it the world’s busiest market, according to Airbus Group SE, Bloomberg reported.

Chinese airlines need to hire almost 100 pilots a week for the next 20 years to meet travel demand. Short of candidates at home, they’re offering attractive pay packages to foreigners with experience — as much as $318,000 a year, according to Bloomberg.

A global pilot shortage was initially thought to a problem only in fast-growing Middle East and Asian markets, but it has spread to North America, Europe, and Africa, Biz Community reported.

In the best case scenario, the world needs about 21,500 new airline pilots a year, or 400 pilots per week. At least half will need to be experienced with globally recognized training and the skills acquired through thousands of hours of airline flying.

Most of the 750 pilots at South African Airways meet these requirements, according to SAA Pilots Association, Biz Community reported.

Pilot training is expensive anywhere in the world, Conroy said. Foreign carriers looking for trained pilots realize that SAA may be a good source. They can get experienced pilots cheap. To make matters worse, SAA is not training any new pilots as it did in the past at its highly successful Cadet Training Programme. The program made substantial inroads in transforming the pilot profession in South Africa, Biz Community reported.

“SAA currently employs 74 of the 83 black airline transport pilot licence holders in South Africa,” Conroy said.

There are aviation colleges training pilots but few pilots are sponsored by airlines in South Africa, and none are sponsored by SAA.