You and up to ten willing creatures of your choice within range assume gaseous forms for the duration, appearing as wisps of cloud. While in this cloud form, a target has a Fly Speed of 300 feet and can hover; it has Immunity to the Prone condition; and it has Resistance to Bludgeoning, Piercing, and Slashing damage. The only actions a target can take in this form are the Dash action or a Magic action to begin reverting to its normal form. Reverting takes 1 minute, during which the target has the Stunned condition. Until the spell ends, the target can revert to cloud form, which also requires a Magic action followed by a 1-minute transformation.
If a target is in cloud form and flying when the effect ends, the target descends 60 feet per round for 1 minute until it lands, which it does safely. If it can’t land after 1 minute, it falls the remaining distance.
* - (a candle)
Interesting that it now specifies Immunity to the Prone condition, but not the Grappled condition.
For DMs that come to this page to check the pace of a party with this spell, here is all the paces
Miles per hour = 600 ÷ 10 = 60MPH(Speed ÷ 10)
Miles per day (Normal pace) = 60 x 8 = 480 MPD (Miles per hour × number of hours traveled (typically 8))
Fast pace = 480 x 1.333333 = 639.999984 = 638 (Miles per day × 1⅓ (round down))
Slow pace = 480 x 2/3 = 320 (Miles per day × 2/3 (round down))