I have a ravpower. I like it. I have never tried using it on a plane and suspect you can't but I like it for non plane use.
I've primarily used it to backup photos from my cards to a USB key or backup drive. The thing I like about it is the iOS interface is just an interface. The files go direct from the card to the drive, there is no file transferred to the iOS device and down to your target. Transfer times are therefore quick.
I've served movies from it to my iPad and it works well.
I used it as a battery backup to power my phone for GPS purposes while travelling.
The interface is not awesome but works. It's finicky at times but you'll have no issue figuring it out. Like all iOS file management apps you have to select images/files and can't copy folders across. That's just a quirk of iOS though and something you're likely used to. You can "select all" though which is nice.
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