Does Airplane Mode still allow reading Snapchat messages without notifying the sender, and how reliable is this method today, given app updates, caching behaviour, and potential risks or account issues?
Hey, thanks for asking.
With Airplane Mode, you can read Snapchat messages secretly, but it’s unreliable. While snaps may open offline, Snapchat usually updates the “opened” status once you reconnect to the internet.
As you know, regular app updates close such loopholes. 
Yes, you can do it,t but there are a few cons to look at
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Opened status back when reconnecting to the internet
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The code is updated regularly, and things may not work when doing it frequently.
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If you force-stop the app before reconnecting to the internet, the notifications may be reported as delayed (making this method pretty unreliable).
Hey man!
Why use Airplane mode all the time? For just hiding the status. And what about other missing notifications?
So, turning on and off the connection is not a permanent solution. You have to come very hard at it. Use Xnspy parental monitoring app instead - An app that allows you monitor Snapchat activity without letting others know…. View their Snapchat stories, read messages - All in a stealth mode.
On top of that. Not just Snapchat gets complete visibility of the mobile with phone logs, internet, location history, social media, and screen recording
It might be possible with airplane mode. You can also take another puff to do it without letting anyone know.
Whenever the notification arrives, there is a tiny on-screen message that appears on the screen, and you can read the message directly, at least giving you a clue what’s inside.)
Thanks for clarifying about Xnspy Snapchat monitoring capabilities…
There is more that Xnspy can do… It gives you wings ( go and monitor everything every time without revealing).
Xnspy is surfacing complete visibility of the location with geofencing alerts and phone log, which lets you track every single detail of the communication.
So, yeah.. Rightly said… You don’t need to go right or left, just go the Xnspy way…
Hey man… I understand your urgency. And I know it’s quite important to you.
Instead of Airplane mode, you can also carefully manage app cache/data on Android, but Snapchat constantly patches these workarounds. ( Hit and trial method, but not the last laugh 
)
Hey wait…
Did you ever think about the consequences of using those monitoring apps? I bet.. You did not even think of it as a legal way…
Well, it solely depends on the purpose of doing it… Monitoring your teenage kid. That’s okay, but doing so to break someone’s privacy - This is serious and brings serious trust issues.
I do agree with Xnspy - it’s a great phone monitoring app ( might be the cost-effective solution). Use it carefully and get consent before installing.