Freshfields represented BAA, having advised its owner Ferrovial when it took the airport operator private in 2006. The firm fielded a large team led by London finance partners Marcus Mackenzie and Ian Falconer.
Clifford Chance advised the lead mandate arranging banks on a series of complex debt restructurings, bond arrangements and loans.
Other firms present on the deal included US firm Latham & Watkins advising Lloyds TSB as liquidity facility provider, CMS Cameron McKenna for the BAA Pension Trustee and Linklaters for the trustee of BAA's existing bonds.
The refinancing deal is one of the largest ever completed for a regulated utility and will fund a £1bn-a-year capital spending programme in BAA's seven UK airports.
BAA had risked having its debt downgraded by credit rating agencies had it not completed the refinancing.
The company is also facing the prospect of being broken up by the competition commission after a report criticised its domination of UK airport services.
Herbert Smith head of competition Elizabeth McKnight is advising BAA on the inquiry.
On the refinancing deal, Freshfields also called on US corporate partner Sarah Murphy, finance partners Edward Evans and Martin Hutchings, UK corporate partner Adrian Maguire and tax partner Sue Porter.
Clifford Chance capital markets partners Steve Curtis, Stewart Dunlop, Lewis Cohen and Emma Matebalavu advised Citi and RBS on the new debt programme.
Also advising the mandated banks were finance partner Andrew Hutchins, trustee partner Sue Rose and derivatives partner Jeremy Walter.