ChatGPT, Sora, and OpenAIs developer-facing API were down on Thursday for more than four hours. OpenAI says it started experiencing a major outage at 11 a.m. PT, but now says its services are slowly coming back online as of 3:16 p.m. PT. Frequent users of ChatGPT may recall that the service went down earlier this month as well.TechCrunch received error messages when attempting to access ChatGPT and Sora on Thursday afternoon. On its status page, OpenAI says the major outage was caused by one of their upstream providers but doesnt offer further detail. As of 2:05 p.m. PT, OpenAI said ChatGPT was partially recovered but users may still experience issues loading their chat history. At 3:16 p.m. PT, Sora became operational again. The company says it is actively working on a full fix for ChatGPT and its API.This is the second time that OpenAIs family of services have gone down during the month of December. When this happened two weeks ago, OpenAI blamed the outage on a new telemetry service gone awry. That outage lasted for roughly 6 hours, an unusually long disruption. Typically, these outages last only an hour or two.Popular services that use OpenAIs API, like Perplexity and Siris Apple Intelligence integration, did not appear to be affected by the outage, according to the companies respective status pages and TechCrunchs testing.TechCrunch has an AI-focused newsletter! Sign up here to get it in your inbox every Wednesday.