On September 27, Apple sent invitations for a press event to be held October 4, 2011, at 10:00 am at the Cupertino headquarters to announce details of the next generation iPhone, which turned out to be iPhone 4S. Over 1 million 4S models were sold in the first 24 hours after its release in October 2011.[29] Due to large volumes of the iPhone being manufactured and its high selling price, Apple became the largest mobile handset vendor in the world by revenue, in 2011, surpassing long-time leader Nokia.[30] American carrier C Spire Wireless announced that it would be carrying the iPhone 4S on October 19, 2011.[31]