The Danish aerial support specialist has been servicing the project since 2002, and has renewed the contract for "three-to-five years" following a tender process. The contract was previously extended in 2007 and has the option for medical services.
The two companies are also in discussion to extend the contract to cover the 288MW DanTysk project, offshore Germany.
Director of Uni-Fly, Jorgen Erik Andersen, confirmed the deal and revealed discussions were on-going for further contracts.
According to its website, Uni-Fly is the only Danish providing hoist operations to wind turbines from helicopters.
Vattenfall holds a 60% share in Horns Rev 1, the first utility-scale offshore wind project. It is made up of 80 Vestas V80-2MW turbines.