iPad Pro (3rd gen) battery drains in airplane mode

Just a couple of notes:

• You can disable Background App Refresh, but you cannot stop apps from running in the background. Those are 2 different things and only the app determines if it contains background processes that will run when the app is not open. In some cases those will also be noted in the Battery Settings.
• Turning off a VPN does not prevent it from running and consuming resources on your device, only removing them will do that.
• Siri usage is for more than using Hey Siri and not sure what "pretty much deactivated" means when it comes to the Siri Settings. Did you shut off Siri Suggestions, which can be done globally or per app?

Turn Siri Suggestions on or off on iPhone - Apple Support

• Age certainly plays a role in your Battery Health. The reported drain over 8-10 hours is slightly higher in my opinion than what you would expect on average, but of course that does vary. I would recommend posting what you see at Settings > Battery where it includes the green battery graph and the top apps consuming the battery.
• In all cases I would recommend to charge your iPad all night, every night and use the Optimized Charging setting.

By how much - and what explicit period of time - are you experiencing unexpected battery drain? Be aware that unless fully shut-down, your iPad still has running processes. Airplane mode, dependent upon other settings, merely shuts-off some radio elements of the iPad.

The rechargeable battery of your third generation iPad Pro will likely be showing its age. The battery capacity may have significantly degraded since it was new. All rechargeable batteries, regardless of battery chemistry, have a finite service lifetime. With every recharge, the internal battery capacity diminishes by a small amount - holder less energy each time. This effect is cumulative; eventually the battery will need to be replaced.

An iPad battery is rated to retain 80% of its original capacity (when new) after 1000 full charge cycles - one charge cycle being any combination of charging that together sums to 100% (e.g. 60 + 20 + 10 + 10 = 100 = 1 full cycle). Rechargeable batteries can be damaged and/or lose significant charge capacity if they are allowed to remain in fully discharged condition for any length or time - and this, ultimately, may impact the service life of a battery.

You might be best advised to seek assistance directly from Apple Support - and request a remote diagnostic test of your iPad. You can contact the Support Team using the Support link at top-right or bottom-left of this page.

Alternatively you can initiate and manage your support cases using the excellent Apple Support App. If not already installed on your iPad, the App can be downloaded from the App Store:

https://apps.apple.com/app/apple-support/id1130498044

You might also visit the Genius Bar at your local Apple Store or Apple Authorised Service Provider (AASP) - where the technicians will be able to test and assess your iPad. Here you will be best placed to explore your available options:

Genius Bar Reservation and Apple Support Options - Apple

For practical purposes, for battery service of qualifying devices, Apple usually exchange the iPad for a renewed/refurbished iPad of the same model and specification. The cost of the exchange is the same as would otherwise be charged for battery replacement.

You can verify both eligibility and cost for your country/region here:

iPad Repair & Service - Apple Support

Given the age of your iPad - and the reduced period of remaining support for your iPad model - battery replacement (if required) might not be an economic proposition. You might instead put this money towards the cost of a much newer model, the performance and capabilities of which will likely surpass your existing iPad Pro.

Mac Jim ID wrote:

In all cases I would recommend to charge your iPad all night, every night and use the Optimized Charging setting.

Not an available feature of the third generation iPad Pro 11".

For iPad Pro models, the Optimised Charging feature requires M4 CPU or later.

LotusPilot wrote:

Not an available feature of the third generation iPad Pro 11".

For iPad Pro models, the Optimised Charging feature requires M4 CPU or later.

You are right, thanks for the correction!