Aetna and the Allegheny Health Network Emergency Group, which employs AHN emergency medicine physicians, have negotiated a three-year agreement that will cover Aetna members in all commercial and Medicare Advantage plans at the seven AHN hospitals. Last month, Aetna and subsidiary Coventry/HealthAmerica sent letters to more than 200,000 members warning that AHN emergency doctors were out of network in a dispute over patient billings with the emergency physician group.