(Adds new details, document)
By Elisabeth O'Leary
MADRID, Jan 22 (Reuters) - Spanish airport operator Aena (IPO-AENA.MC) is poised to increase the price range of its planned partial listing by up to 2 euros per share, a source with direct knowledge of the matter said, in a move that could force core investors to pay more than envisaged or miss out.
The higher price is the result of the company's strong business outlook, which has added between 200 million and 300 million euros ($344 million) to the valuation made when it first intended to list last October, the source said on Thursday.
The valuation of the company is now more likely to be between 6.4 billion euros and 8.3 billion euros, sources familiar with the company said, compared to an earlier range of 6.2 billion to 8 billion euros.
The sale of 49 percent of Aena, with the state keeping the remainder, stalled in November amid adverse market conditions and political wrangling over the handling of the offering, with several ministers and advisers said to have asked for more time.
The listing is now back on track and Aena, which handles 187 million passengers through its mostly European airports, could benefit from a recovering Spanish economy, cheaper oil prices for airlines and a better outlook for tourism.
The IPO prospectus, outlining a price range and outlook, will be published on Friday subject to the government's final blessing.
The stock is slated to trade for the first time on Feb 11.
Core shareholders Corporacion Financiera Alba, British fund TCI and Ferrovial had offered to buy stakes at 53.5 euros per share, 51.60 euros and 48.66 euros respectively in a first phase in which a total 21 percent stake was on the block.
But Aena has since published nine-month results bearing the fruits of a huge restructuring over the past three years. Core earnings (EBITDA) rose 15.5 percent to 1.46 billion euros, boosted by higher traffic as Spain pulls out of recession.
A sale document seen by Reuters shows that in the case the final price, expected on Feb 9, is higher than those offered by the core trio, Enaire, Aena's holding company, would have several options.
One could be to sell more shares to a shareholder, such as TCI, that bid to buy more than it was initially apportioned. Another could see core shareholders bidding to buy shares in the book building process alongside other institutional shareholders.
Book building for the second part of the sale, in which a further 28 percent of the group will be sold, will kick off with a series of roadshows on Monday 26 January. ($1 = 0.8724 euros) (Editing by Julien Toyer and Vincent Baby)