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For more information on this, take a look at:
Wi-Fi: How to troubleshoot Wi-Fi connectivity
Symptom: The network connection drops unexpectedly
- Your Mac may not not stay connected to your Wi-Fi network reliably.
- Your Mac may stop accessing the Internet during use.
Use these steps if your computer disconnects from its Wi-Fi network unexpectedly.
- Check your range to the Wi-Fi router and reduce the effect of interference.If your computer is too far from your Wi-Fi router or your environment has too much Wi-Fi interference, then your computer may not detect the Wi-Fi network properly. The easiest way to check for range limits with your Wi-Fi network is to move your computer or your Wi-Fi router closer together and make sure that there are no obstructions (such as walls, cabinets, and so forth) between the router and your computer.See Potential sources of wireless interference for more information about interference and solutions.
- Try connecting to a different Wi-Fi network. If your computer works fine when connected to a different Wi-Fi network, then the issue may be related to your network router or ISP. In that case, contact the manufacturer of your router or your ISP.
Best of luck,
Some more information. The first one contains an update for the MacBook AIr.