For those writing "Not available in [one_of_the_EU_countries]", it won't!
The developer has made an explicit choice of releasing Delta only on the AltStore in EU.
While, for example, people from US will be able to install Delta on both iPhone and iPad, from the official Apple App Store, EU people can only install it from the Alt Store, and because the alternative stores are only available on iPhone and not iPad, EU users won't be able to install it on the iPad.
I'm pretty sure the developer will blame this on Apple, while he clearly made a choice of not giving a choice to the users.
Wanna charge money for Delta? Absolutely fine! Wanna make it 30% more expensive on App Store, to cover Apple fees? Fine as well. But give users a choice and don't force them to install it from an alt store, and most important don't slap iPad users in the face like this!