The helicopter crew asked permission to use a practice called "visual separation" - which allows pilots to take control of navigation around other aircraft instead of relying on the controller's guidance. However, the practice has its limitations, including poor visibility and limited range of vision from the cockpit. The request was approved by traffic controllers about two minutes before the accident, but the report revealed that the technique was not executed properly. After the visual separation was activated, radio communication between the pilots and the controller was broken.