Kind of a bizarre card, in that it's nearly identical to Born Aloft and even came in the same cycle. The only distinctions are that this is an event rather than an attachment, so you don't have to anticipate needing it in the planning phase, and it only applies to eagles rather than all allies. In practice, you can almost always predict which ally is going to want the effect, and eagles are a very small subset of allies, making Meneldor's Flight straight-up inferior to Born Aloft.

In any case, common uses:

Spamming Descendant of Thorondor
Getting cards onto Eagles of the Misty Mountains in a pinch
Immediately usable if you draw it after the planning phase, or play eagles outside of the planning phase
That's about it... It's a really lame card.

I don't think I'll use this card very often, even in a dedicated Eagle deck. I don't see a lot of good uses for it. Maybe it's useful if you can't pay the resource cost to keep a Vassal of the Windlord or Winged Guardian in play, because you can play it in the action window that comes between combat damage and the attack ending and then pay the resources to put it back into play next round. I guess it also powers up your Eagles of the Misty Mountains whenever you want, but that seems like a waste because you lose the Eagle that you returned to your hand. Admittedly it does seem cool to pick up and play Descendant of Thorondor over and over, but that's expensive unless you have cost reduction like Radagast's Staff (which came out near the end of the game's life cycle and this card came out near the beginning). So I guess if there were more cards that cared about when Eagles entered or left play (kind of like a Tactics version of what the Silvan play style ended up being), then maybe this card would have been more useful. But as it is, the card isn't that great.