This app was mentioned in 3 comments, with an average of 2.00 upvotes
I've been using FlightView (which has a free version) for a few years now. I always went back to it because it seemed to be the only app that you could enter in flight data even months in advance.
Rough around the edges, could use some features, but works well with what it does.
I own the paid version, updated 2 years ago, but it's no longer on the Play Store. I suspect they've moved to IAP or subscription. Here's the link to the free version, updated last month. https://play.google.com/store/apps/details?id=com.flightview.flightview_free
On my last trip I used Google Trips in conjunction with FlightView.
Google Trips has updated a bit more and now has the ability to add destinations, but it still misses some key traveling features. Such as editing flight info (adding seats, etc) and sometimes trips don't show up.