"There is an art, or rather, a knack to flying. The knack lies in learning how to throw yourself at the ground and miss." -- The Hitchiker's Guide to the Galaxy
Adapting this to DFRPG, I propose that one way to achieve flight is to cast a block against hitting the ground on yourself.
Ok, that was a joke, but perhaps not entirely. It seems to me that you could adapt the block rules to basically subtract shifts from the stress you'd normally take from a fall. So, for example, a 30 foot fall results in 15 stress, but if you put up an 8-shift block against falling damage, then that might reduce it to a 7 stress hit, which greatly reduces the severity of the consequence you'll take.
That said, I think a better way of handling this, which seems to me to be more in line with the way the designers do things, is to use some of the benefits of Thaumaturgy. Basically, you want to set up a Thaumaturgical 'sprint' to get from the top of the building to the bottom of the building: ie, a sufficiently high sprint result (Athletics simple action) combined with 'Solve Improbable or Impossible Problems' to allow you to ignore the fact that you're running on air. In short, almost the same as Dresden's escape potion.
So, basically you just determine how many 'zones' of travel you'd need to cover to get to the ground, and this is the number of shifts worth of sprinting you need. (Well, actually you can subtract one, since the first zone is 'free'.) Perhaps one zone per floor would be a reasonable rule of thumb.