Can I use my Treo on an airplane

From TreoCentral

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A: Yes, the Treo essentially has two modes that can operate independently: organizer mode and wireless (phone, SMS, email, web browsing) mode. If you choose to save your battery life and turn your wireless mode off, you can still access all of your organizer functions. Another reason to have wireless off besides conserving battery is when you are on an airplane and are required to turn off your phone, you still have access to your organizer and PalmOS applications.

To turn off your phone, simply hold down the Power button until you see the splash screen for your wireless carrier. The antenna icon will no longer appear at the top of your screen.

It is also a good idea to turn off Bluetooth.