After Hurricane Maria ravaged Puerto Rico last fall, the island converted to a purely cash economy, a recent article by the Atlanta Federal Reserve reports.

The hurricane struck the U.S. territory on Sept. 20, just two weeks after Irma had hit. During September and October, the Federal Reserve supplied more than $1 billion to Puerto Rico’s financial institutions, seven times the amount the Fed paid out to the island’s banks in the same period in 2016, according to the Federal Reserve Bank of New York.

The category 5 Hurricane Maria knocked out electricity throughout Puerto Rico. The island’s 3.4 million residents could not use a debit or credit card, nor could they make online payments of any kind.

The New York Fed—the Federal Reserve’s busiest cash shop in terms of handling overseas currency distribution—typically supplies currency to Puerto Rico’s financial institutions. But Maria disabled the island’s airports, so no commercial flights could land for days after the hurricane hit. Even as flights resumed, planes from New York could not travel to Puerto Rico—only daylight arrivals and departures were possible because of damaged airport equipment.

Planes from Florida could meet the daylight requirement, however, so the Atlanta Fed’s Miami cash operation stepped in. Starting with a chartered plane out of Orlando on Sept. 26, the Atlanta Fed’s Miami Branch shipped $670 million in currency to Puerto Rico in the two weeks after Maria struck. After another chartered flight out of Fort Lauderdale on Sept. 27, commercial flights resumed normal transport of currency.

Cash contingency was not the only role the Atlanta Fed played after Maria. The Miami Branch’s regional executive, Karen Gilmore, fielded calls from businesspeople and bankers with operations in Puerto Rico who were concerned about getting cash to their employees on the island.