I have two iPad Air tablet. After the iOs has been upgraded to 10.0.0 and later to latest iOS 10.0.2, the WiFi cannot be connected to any WiFi router after overnight charge. I have to power-cycle the iPads to make the WiFi work again. I know it is not my routers problem, because the same routers can be connected by the third iPad Air2. Also the same routers can be connected by other Android devices and Windows PC laptops.
It seems that the problem only happens on iPad Air, since I never saw the same problem on iPad Air2. As I said, I had two iPad Air tablets. At middle night, I put these two iPad Air in charge, and then around 6:30 am in the morning, I start to use the iPads, but there is no WiFi connection. It cannot connect to any router or hotspots. The ip address is always in APIPA, 169.254.0.0. It does not recover even after I turn off/on iPad wifi, or get into Airplan mode, and disable airplan mode. Cannot connect to home routers or public routers. The only way to recover it is to power off the iPad air device, and then power on again.
The two iPad Airs did not have such problem at all before iOs 10 upgrade. So I believe the root cause is in iOS10, the software, not the hardware.
By the way, I tried to set one of my iPad Air to static IP address, this does not help. I also tried to renew the lease, did not help either.
I always turn off Bluetooth while WiFi is on.
Also the problem does not happen every morning, but happens on most of mornings. It looks like the WiFi gets into deep sleep mode after overnight charge.
I myself am very knowledgeable about WiFi Networking and working in this area in another company in Sunnyvale CA. Please let me know if anyone from Apple team wants to know more about this report.
If anyone from Apple develop team wants to know the iPad Air model number, I could provide it.