In modern air travel, you generally do not need to show a physical, printed itinerary at the airport, but having a digital version accessible is highly recommended for several stages of your journey. When checking in at a kiosk or a staffed desk, your passport or government-issued photo ID is usually sufficient for the airline to pull up your booking in their system. However, showing your itinerary can be essential if you are traveling internationally to countries that require proof of onward or return travel before allowing entry. Furthermore, while security checkpoints typically only require your boarding pass (on your phone or paper), having your itinerary ready can help resolve discrepancies if there are issues with your ticket or if you are entering a terminal that restricts access to ticketed passengers only. It is a best practice to keep a screenshot of your flight details and confirmation number on your mobile device to ensure you can access the information even without a reliable internet connection or in the event of a dead battery.