By Matthew Cowley and Paulo Winterstein 
 

SAO PAULO--Singaporean, Swiss and German companies on Friday won the rights to operate two of Brazil's largest airports in an important boost to the government's efforts to hand over large parts of the country's struggling infrastructure to the private sector.

A huge bid for Rio de Janeiro's international airport by Brazilian engineering firm Odebrecht SA and Singapore's Changi Airport Group Ltd. brought gasps of surprise and disbelief from participants in the auction held at the Sao Paulo stock exchange.

The two partners offered 19 billion Brazilian reais ($8.3 billion) to the government for the right to operate one of Brazil's main gateway airports for the next 25 years. That was nearly four times more than the minimum bid of BRL4.8 billion, and 31% more than the second-placed bidder.

There were no follow-up bids from the four other firms that were in contention for the airport, Galeao.

The size of the bid is a lift for the administration of President Dilma Rousseff, often criticized for its interventionist approach to the economy that some say has deterred private-sector interest in infrastructure concessions. With the country's decades-old transportation network seen as a major bottleneck for faster economic growth, the government has sought to bring in the private sector to accelerate investments in ports, airports, highways and other areas.

"We have today a great demonstration of confidence in the future of Brazil," said Brazil Aviation Secretary Moreira Franco.

Friday's auction also saw the government sell the rights to operate for 30 years the Confins airport in the city of Belo Horizonte, in Minas Gerais state, after a heated open-cry battle that saw a group led by Brazilian infrastructure operator CCR SA (CCRO3.BR) prevail over another group including Construtora Queiroz Galvao SA and Spain's Ferrovial Aeropuertos SA.

CCR and its partners in the Aerobrasil consortium, Switzerland's Flughafen Zuerich AG (FHZN.EB, FLGZY) and Germany's FMG Flughafen Munchen GmbH, won with a bid of BRL1.82 billion.

Airport traffic in Brazil is expected to soar in coming years. The airport in Rio, Brazil's second largest after the international airport in Sao Paulo, handled 17.5 million passengers in 2012 and that is expected to rise to 60 million in 2038, according to the government.

As well as the money promised in the auction, the successful bidders will have to hand over a fee equal to 5% of annual gross revenue to the government for the lifetime of the concession.

Odebrecht and Changi will have to invest about BRL5.7 billion in the Rio airport to provide an extra independent parallel runway, expand the aircraft apron--a sort of parking lot for airplanes--as well as provide new cargo storage areas and car parking facilities.

In Belo Horizonte, the winning bidders will have to invest an estimated BRL3.5 billion to build a new terminal, a second runway, and expand the apron. Confins is the fifth-largest airport in Brazil, and passenger traffic is seen rising from 10.4 million passengers in 2012 to 43 million by 2043.

Write to Matthew Cowley at Matthew.Cowley@wsj.com and Paulo Winterstein at Paulo.Winterstein@wsj.com

Subscribe to WSJ: http://online.wsj.com?mod=djnwires