As soon as a player rolls a 1, the creature will no longer be granted flying from Drop Tower. No player may take any actions between the result of die roll coming up 1 and the flying effect ending.

You can choose Drop Tower’s effect for Grand Marshal Macie’s last ability. If you do, the effect won’t end even if a player rolls a 1, though if that happens, the effect will end as soon as Grand Marshal Macie untaps.