Hello Kellydogwoof,
If I'm understanding you right, you're hearing notification sounds and alerts from your iPhone at night when you have Airplane Mode enabled. I'm happy to help you out with this.
Airplane mode is designed to quickly disable wireless features on your device to comply with airline regulations; however, using it does not mean it would not be possible for you to still receive notifications and alerts from certain apps. It's also possible to enable Wi-Fi and/or Bluetooth while Airplane Mode is turned on, which would mean there is even more chances of getting notifications and alerts while you're sleeping. You can view more about that here: Use Airplane Mode on your iPhone, iPad, iPod touch, and Apple Watch.
If your purpose of using Airplane Mode at night is to silence calls, alerts, and other notifications, the best option would be to use Do Not Disturb instead. With Do Not Disturb, you can silence your iPhone and even schedule a specific timeframe for it to be enabled. When Bedtime is enabled, calls and notifications are silenced, the Lock screen is dimmed, and notifications will appear under During Bedtime in the Notification Center until your scheduled Do Not Disturb ends. Here's information about how to enable Do Not Disturb and adjust its settings: Use Do Not Disturb on your iPhone, iPad, and iPod touch.
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Take care!