The FAA will use key mission “triggers” such as the loading of rocket fuel and the final disposition of the booster rocket to pinpoint when to close and reopen airspace.·

For the first time, the FAA will implement time-based procedures for a launch from Boca Chica. This will identify and reroute only the aircraft directly affected by the closed airspace allowing more aircraft to stay on their most optimal and efficient routes. It has previously only been used for launches from the Florida space coast.

Both the Starship vehicle and the Super Heavy booster rocket will transmit telemetry data to the FAA via the Space Data Integrator tool. Data such as position, altitude, speed and any deviation from its expected flight path will provide the FAA situational awareness, and in combination with other information, help to reopen airspace quicker.

https://www.theverge.com/2023/4/14/23684043/spacex-starship-faa-launch-license