Tap the Signal icon then tap Comm Manager. Open Comm Manager, then tap the Flight Mode button to enable flight mode. This turns off all wireless radios on your device, which include the phone function, Bluetooth, and Wi-Fi. To resume call function, disable flight mode by tapping the Flight Mode button again. This also restores the previous state of Bluetooth and Wi-Fi.
This information can be found on page 28 and 80 of the user manual. If you don't have a copy of the user manual, you can download it here in our website from the HTC Mogul product page.