A question on the rules of Feather Fall

I have a situation where a flying mount was knocked prone, and would have fallen if the character riding it hadn't cast Feather Fall. However it was only knocked prone until it's turn, and then the mount used half it's movement to right itself, and then keep flying. I ruled the half movement as if it was shaking off the disorientation, rather than actually getting up off the ground. However the next round of combat the flying mount was knocked prone again. The argument was about the wording of Feather Fall.

Since the creature stopped falling when it started flying again, does the spell end early? Or does the spell continue since it never touched the ground?

If the spell ended early, then the mount and rider should have fallen to the ground the second time it was knocked prone. If the spell continued, then they didn't fall to the ground and only fell another 60 feet. This battle was taking place roughly 400 feet above a forest, so they would have taken max fall damage of 20d6, so they were arguing that the Feather Fall never ended since the creature never touched the ground. As the DM I specified that I was ruling it this time as if the Feather Fall was still active, but said I'd review it for any possible future interactions.

I'm curious how other DMs would rule on this interaction. Do you think I was correct in saying the Feather Fall was still active due to not touching the ground, or do you think the spell ended when the creature stopped falling and started flying again?

Feather Fall lasts for 1 minute or until the creature ends. If they don't land, the spell lasts for the duration. RAW, you made the correct ruling.

The spell doesn't end when falling stops. It ends after 1 minute or if you land. Landing means touching ground or any surface after descending. 

Since the target did not land and it was less than a minute, then Feather Fall would still be in effect.