CORPORACIÓN FINANCIERA ALBA, S.A. 
The sale of a 49 percent stake in the world's biggest airports operator was flagged as the largest initial public offering in Europe this year and a litmus test for domestic investor faith in an economic recovery.
Analysts estimate Aena's enterprise value at around 16 billion euros, 12 billion euros of which is debt.
But demand has been tepid amid a glut of European stock market debuts this year, limitations on shareholders by the state and financial restrictions on infrastructure funds.
Enaire, the state holding company which owns Aena will announce on Monday or Tuesday the names of the two to four shareholders who will buy a total of 21 percent of the airports operator. The deadline for binding offers was Wednesday lunchtime.
The other 28 percent is to be sold to domestic and foreign investors, primarily financial institutions, and the listing is set for late November.
"Some investors that were in the initial list have withdrawn from the race," said a source with direct knowledge of the matter.
The source said the final list of contenders should include Corporacion Alba (>> Corporacion Financiera Alba SA), Ferrovial (>> Ferrovial SA), the Children's Investment Fund Management and Norges Bank Investment Management, as reported earlier on Wednesday by business daily Expansion.
Corporacion Alba confirmed to Reuters it had put in a bid. Ferrovial and Norges Bank Investment Management declined to comment while the Children's Investment Fund Management could not be reached for comment.
Enaire declined to comment.
The four bids, if confirmed, would be below the "six or seven" institutional investors the Spanish government had said last month would make an offer.
SWEETENER
Public Works Minister Ana Pastor offered a last minute sweetener for the sale on Tuesday when she said investors would be given a seat on the company's board.
But one banker who has looked into the offering said some funds stepped away because the sale carried a one year lock-up period imposed by the state while others in general do not want to invest in listed companies because they have to mark their stake to market.
Other investors declined to participate because they want to control the strategy of the companies they invest in, the sources close to the process also said.
The operation, which is being handled by investment banks Santander, BBVA, Morgan Stanley, Goldman Sachs and Bank of America Merrill Lynch, required a minimum investment of 250 million euros.
The banker said investors fatigue for European and Spanish listings and weaker financial conditions were also to blame.
"We didn't see any real interest either from the strategic funds or from industrial investors," said the banker, who is not involved in the process. "We have a lot of doubts."
Aena operates 46 airports in Spain, has stakes in many Latin American airports and will soon also hold a majority stake in Luton airport in Britain.
The group made a profit of 715 million euros in 2013, while its airports division made a first-time profit of 597 million euros due to a recovery in passenger traffic after Spain returned to growth last year following a long recession.
Turnover was also backed up by a reduction in group costs to 1.86 billion euros in 2013 from 2.02 billion euros in 2012 and higher airport and navigation tariffs.
The share sale, expected to include an offer of shares to the public, will be given a green light by the stocks commission around Oct. 23, sources familiar with the process said.
(Writing by Julien Toyer, editing by David Evans)
By Robert Hetz and Elisabeth O'Leary
