How to get a lot of Flightstones fast?

I'm curious, what are the most effective strategies for quickly accumulating a large number of Flightstones? Are there any specific missions, events, or in-game activities that offer a higher reward rate for Flightstones? Additionally, are there any tips or tricks that seasoned players use to maximize their Flightstone earnings? I'm eager to learn more about how to efficiently accumulate this valuable resource and progress further in the game.