Shares in state-owned Spanish airports group Aena took off after they went on sale in Madrid. They rose close to 20 percent from the initial public offering (IPO) price.

There was strong demand from investors betting on the country’s economic recovery. The IPO was more than five times oversubscribed.

The Madrid government is raising close to four billion euros with the sale of a minority stake. It plans to keep control with at least 51 percent.

The money will be used to pay down public debt.

The company runs 46 Spanish airports and has stakes in London’s Luton Airport and others in Mexico and Colombia. It handles 187 million passengers a year.

The sale, which was Europe’s largest initial public offering since 2011, was postponed last October, hit by demands for more transparency.

A political hot potato because of regional politics, the sale has been an on-off project for years.

The government said its success was a sign the economy was emerging from a six-year crisis.