France's Ardian prepares sale of Luton Airport stake -sources

* Ardian's stake expected to be worth $400 mln-plus

* Spanish airports operator Aena owns 51 pct

* Aena has right to buy out Ardian

By Clara Denina and Dasha Afanasieva

LONDON, March 20 (Reuters) - French private investmentcompany Ardian has hired Rothschild to sell its 49percent stake in Britain's fifth-biggest airport, Luton, bankingsources told Reuters.

Ardian and Spanish airport operator Aena, whichowns the other 51 percent, bought the airport from toll operatorAbertis in 2013 for 508 million euros ($626 million).

Aena has a preferential right to buy Ardian's stake, whichwill be valued at more than $400 million, the sources said.

At a management meeting with sell-side analysts this monthAena's chairman said the company is not interested in buying outArdian's stake in Luton at any price, but sees it as anopportunity to provide an entry to a new financial partner.

A spokesman for Aena declined to comment further whileArdian declined to comment and Rothschild did not respondimmediately to a request for comment.

European airports have been a lucrative business for privateequity firms and pension funds over the past few years becausethey offer strong growth potential from increasing global traveland services such as shops, on-site hotels and car parking.

Banking sources expect infrastructure fund GlobalInfrastructure Partners to sell investments in Edinburgh andGatwick airports in the coming year or two in what could be atest of investor sentiment on the eve of Britain's exit from theEuropean Union.

VALUATION GUIDE

Luton's valuation will help to guide potential deals forthose other British airports.

London City, an airport favoured by business executivesbecause of its proximity to London's financial districts, wassold to a pension funds consortium in 2016 at a valuation ofmore than 2 billion pounds ($2.8 billion), more than 30 timescore earnings and a threefold increase from the price paid bythe owners a decade earlier.

In 2014 Luton gained approval for expansion of the airportand its runaway to boost capacity and attract budget airlinesincluding Wizz Air and Easy Jet.

Almost 16 million passengers travelled to and from theairport last year, the airport's website says.

In the year to March 2017 Luton airport generated earningsbefore interest, tax, depreciation and amortisation (EBITDA) of52.6 million pounds.

Ardian, which handles $65 billion of assets across Europe,North America and Asia, recently sold a stake in industrialengineering group Fives and launched a sale of German healthcarebusiness Riemser Pharma. Sources have said it is alsoconsidering a sale of Italian chemicals maker Italmatch.($1 = 0.7163 pounds)($1 = 0.8114 euros)(Reporting by Clara Denina and Dasha AfanasievaAdditional reporting by Andres Gonzalez in MadridEditing by David Goodman)