MILAN, May 13 (Reuters) - Italian infrastructure group Atlantia on Thursday confirmed its 2021 guidance after reporting a 67 million euro ($81 million) net loss for the first quarter as the pandemic continued to bite. The group controlled by Italy’s Benetton family recorded an 8% fall in sales between January and March due to the prolonged impact of the healthcare crisis on motorway and airport traffic. Atlantia owns Italy’s biggest toll-road operator, Autostrade per l’Italia. It is due to decide by June 11 whether to accept an offer for its 88% stake in Autostrade it has received from state lender CDP and other investors. ($1 = 0.8289 euros) (Reporting by Francesca Landini; editing by Valentina Za) Our Standards: The Thomson Reuters Trust Principles.