Apple is having trouble retaining top talent in its Maps division.

We’re told that a notable number of exits have occurred on the Maps team over the last several months with a large portion of those engineers heading to ride-sharing startup Uber. The most notable Apple employee to recently depart is Brad Moore, who exited in October to become a manager at Uber. As “Senior Engineering Manager, Maps Apps & Community” at Apple, Moore “built and managed the application and community teams responsible for Maps on iPhone, iPad, CarPlay, OS X, and Apple Watch,” according to LinkedIn.

Since Moore was in charge of such a critical application across all of Apple’s major hardware and software platforms, his departure marks a significant loss for Apple and a huge gain for Uber. Apple is said to also be overhauling its public transportation team following the group’s inability to launch the planned directions service for iOS 8 last year. Sources say that Apple’s Maps team is also progressing on its testing in major districts like New York City of a new indoor mapping service. Chris Blumenberg, another former top Apple Maps manager at Apple, left for Uber in July.