Hi,
I have an iPhone 5 (iOS 7 and 8). Twice a year I fly and use Airplane mode. When I get back home after a few hrs of use Safari will no longer connect to the internet. So I reset my DSL modem and Router. Then I reset the iPhone's network settings which requires re-entering all the setting for Wi-Fi network access. If Safari still does not connect I check to see if the Apple Store App, iTunes and Mail work (they usually do). I then look at an email with graphics. If the graphics do not show but the text does, then the problem is that Safari is timing out to early to see all the data from a server. This is verified by repeatedly click the re-load button. When the page eventually loads it indicates a timeout problem. I then check to see what services are active. Although I have LET on Verizon in my area it creates problems for Safari. So I turn that off. I also turn off cellular data access so If Safari does work I will know that it isn't defaulting to cellular data when Wi-Fi access fails. I go back to Mail and it now loads the graphics as well as the text. I open simple small web pages. Safari is now working. Open a complex graphic intense page and after 2 tries it now loads the page. This process has fixed my Safari problems every time.
The last thing I do is turn cellular data access back on so I have access to the internet when not near the house Wi-Fi network.