The Cushioning Charm creates an invisible “pillow” on the handle of a broom to make flying more comfortable (QA9). This spell can be used for a soft landing during an escape.
Hermione cast a Cushioning Charm for protection when she, Bogrod, Harry, Ron, and Griphook were thrown from a Gringotts cart and fell a great distance (DH26). Albus Potter and Scorpius Malfoy used the incantation “Molliare” as they leaped from the roof of the Hogwart’s Express as the Trolley Lady tried to stop them (CC1.11).
History and Notes
The Cusioning Charm was Invented by Elliot Smethwyk in 1820, making riding a broom a lot more comfortable (QA9).
Molliare from Latin "mollio" meaning "soft"Arresto Momentum from Old French arester "to stay, stop" + Latin momentum = "movement"
In the film for Deathly Hallows Part 2: Hermione uses the incantation "Arresto Momentum" to save them when they fell from the Gringotts cart. However, the book does not use this incantation, instead it only mentions that the spell was the Cushioning Charm. So is the Cushioning Charm's incantation "Arresto Momentum"?
The films are not considered to be canon, since they were not written by Rowling. Her mention of the term "Cushioning Charm" in Quidditch Through the Ages and the accompanying illustration show that the spell creates what is essentially an invisible pillow on the handle of a broom, which is very different from the effect we see with "Arresto Momentum": slowing something's fall. That would suggest that the scriptwriter's use of the term "Cushioning Charm" in the film is an error.
Adding to the confusion, the Cushioning Charm is shown as slowing someone's fall and is given the incantation "Molliare" in Cursed Child -- but that play, while considered to be canon even by Rowling herself, wasn't written by her.
So which is it? Is the Cushioning Charm the same as Arresto Momentum? Are there two spells both called that name which different effects, or possibly variations of the basic spell? There is no way to be sure.