At least once a month - and sometimes up to three times a week - a private plane lands in a secure area of Robert Gabriel Mugabe International Airport on the outskirts of Zimbabwe's capital, Harare, carrying millions of US dollars. The pallets of cash are unloaded, divided into packages and then distributed to transfer points around the country.

This unusual but legal operation, organized by the country's largest mobile money app, Mukuru, illustrates just how far companies will go to satisfy customers looking to avoid the local currency in one of the world's most fragile economies.

The digital money sector in Africa has grown exponentially over the last two decades and is already worth around 912 billion dollars a year, according to the GSMA, a global research and lobbying group for mobile operators. But while most fintechs focus on sending money digitally, those in Zimbabwe also fill a different niche: helping Zimbabweans get their hands on physical US dollars.

"Demand for dollars is very strong in Zimbabwe," says Ross Martin, commercial manager for Africa at Travelex Ltd, one of the world's largest foreign exchange companies. In the first five months of the year, remittances from Zimbabweans living outside the country rose 16% to 823 million dollars, according to the Reserve Bank of Zimbabwe.

The country's preference for cash began more than 15 years ago, after a failed land reform policy triggered a spiral of hyperinflation that wiped out Zimbabweans' savings and led to the disappearance of the national currency in 2009.

"During hyperinflation, people dispose of their local currencies like hot potatoes," explains Steve Hanke, Professor of Applied Economics at Johns Hopkins University. In the midst of one of these episodes, the US dollar became king.

Since then, the government has made six attempts to re-establish a national currency, the latest being a gold-backed unit known as the ZiG. When it was launched in April, 80% to 85% of all transactions in Zimbabwe were in US dollars, according to the national statistics agency. Although the new currency has remained stable so far, it has been an uphill battle to get people to adopt it.

"Since I have foreign currency, I don't have to worry about the devaluation of the currency," explained Maureen Nyoni, 68, while receiving her children's remittances in the UK from a Mukuru agent in Harare.

The preference for cash doesn't just reflect concerns about ZiG's stability. The government has a history of converting foreign dollars deposited in banks into local currency without warning and imposing strict limits on withdrawals - which has scared Zimbabweans away from the formal banking sector.

Most of the 1.9 billion dollars in transfers sent to Zimbabwe last year were made through Mukuru, the country's largest money transfer service, with competitors Mama Money, hellopaisa and informal means accounting for a significant percentage of the rest. Last year, Mukuru served seven million active customers in all its markets, from Lesotho to Kenya, but only sends money to Zimbabwe, which accounts for almost half of its turnover.

"If we want to be relevant in a tech or fintech environment in Africa," says Andrew Jury, CEO of Mukuru, "we have to have these strong avenues of money in and out." (Bloomberg. Image: DR)