At subsonic speeds, airlines have been slowing planes down to save fuel. There have been significant investments in data collection at all phases of flight resulting in models of the most fuel efficient way to fly. For example, Rolls Royce has a case study with Microsoft where they used AI models to teach pilots how to fly in a way that would save more fuel.

https://www.zdnet.com/article/microsofts-azure-iot-takes-to-...