OpenAI reported Thursday that its ChatGPT assistant, Sora video generator, and developer programming interface resumed operation after over four hours of downtime. The outage followed a surge in demand for Sora, which CEO Sam Altman acknowledged on Tuesday. ChatGPT has gained massive popularity, with 300 million weekly active users. On Wednesday, Apple launched new software updates integrating ChatGPT into its iPhone, iPad, and Mac platforms. OpenAI is valued at over $150 billion in an October funding round backed by Microsoft and Nvidia.