Yes, leaving your phone on airplane mode while abroad is a highly effective way to avoid expensive international roaming charges. When airplane mode is active, your phone's cellular radio is completely disabled, meaning it cannot send or receive calls or texts via mobile towers. However, you can manually re-enable Wi-Fi and Bluetooth while staying in airplane mode. This allows you to connect to hotel or cafe Wi-Fi to use internet-based apps like WhatsApp, Google Maps, and social media without the risk of "background data" triggering a daily roaming fee from your home carrier. Your phone's GPS will also continue to function in airplane mode, which is invaluable for navigation if you have downloaded offline maps. This is the gold standard for budget-conscious travelers who want to use their device as a camera and mini-computer without the fear of returning home to a "bill shock" involving hundreds of dollars in unexpected data usage fees.