Over the course of playing RuneQuest there has been some problems with magical flight, especially the sorcerous version. How high can one go? What are the differences between the various versions? What are the effects of wind? If you have Fly cast can use use it to avoid a pittrap? And on and on. These are the house rules I use for flying in Glorantha.
I do admit, however, that my knowledge of flying in the Real World is limited, so if anyone has any suggestions on how to shuffle these numbers, or exact details on how high certain things can fly, then that'd be great.
As a house rule, if one wishes to use the magical flying to escape a different element, such as being trapped in a lake or the ocean, then at least half of one's body has to be out of the element, like the abdomen, both arms the head. Of course there is nothing to stop a powerful, high intensity Fly being cast on a small object, like a dagger, which is held out of the water and used to drag the character out - although few sorcerors have the foresight for such things.
Secondly, there are analogous spells for travelling through the other elements. They are rare, but are effectively the same as Fly and Flight. So there is an equivalent for travelling through water, allowing fast propulsion underwater, one for travelling through the underworld, allowing "flight" in the underworld, and the same for the Sky. There is the even rarer spell that allows travel through the earth, where one can literally sink in and walk around. None of these spells bestow any ability to survive the conditions there, however, so you'd still suffocate travelling through earth or water (no-one has to breath in the Underworld or the Sky Realm for Time and all natural laws do not hold there).
The sorcerous version of Fly allows one to reach a height of 50m per level of intensity of the spell. This means that limited sorcerors won't be able to fly to mountain tops unaided. Powerful sorcerors, however, will be able to fly very high indeed - through invoking St. Josselyne and St. Malkion to enhance their magic it is not inconceivable to reach intensity 50 Fly, or higher! This can be achieve even more height than normal Rune Magic.
The Rune Magic spell Flight will allow one to travel to 4000m above the ground, which is stunningly enough, high enough for most purposes. Under certain conditions, and in certain places, this ceiling can be increased. On Orlanth's High Holy Day is increases threefold to 12,000m which is high enough to reach the peak of Kerofinela. The same effect occurs near Stormwalk Mountain, the area itself enchances the magic. However, if you want to travel higher and break the ceiling, travelling far above into Middle Air then you will have to use the Vanganth spell Into Middle Air.
The rare shamanic gift that allows one to fly (see below) allows one to reach a height of 100m for the first level, and then 200m for every level thereafter.
The mystic power of skyriding, which bestows a horse with the ability to fly (see Sandy Petersen's Mysticism rules), grants it the ability to travel at a height of 2000m, which is a good guideline for any flying creature including Wind Children.
Non-divine powered flight has certain problems with winds over a light win (wind STR 18). Once the wind exceeds this level, beings powered by such magical flight get whipped around, caught on the wind gusts and dragged off wherever the winds blow them. Once a wind exceeds STR 18 there is a chance of this occuring, depending upon the intensity of the spell used (for the purposes of the shamanic gift, the intensity is the square of the level of the gift, so a level 5 gift counts as intensity 25 for these purposes). If the character is using a spell with an intensity less than half the wind STR, then they cannot move safely. If the character does have a spell with an intensity higher than half the wind STR then they can move safely. Characters who attempt to move unsafely must, every round, match the intensity of their spell against the wind STR. If they fail, they are whipped off into the wind streams. Sometimes this is just a pain, blown off course. Sometimes it can be hazardous, being blown into buildings and such. In some places it is almost fatal, on mountain tops where the wind blows hard on can easily be blown off into the upper reaches of Middle Air, buffetted about to pieces.
Divine Magic flight can safely travel though any non-storm environment, although they will still suffer the usualy penalties for exposure and visibility. In storms they stand the normal chances of damage, unless they use the Vanganthi spell Avoid Storms.
Sylphs, and other air elementals, can be used as a mode of transport. However, for long periods of travelling the effect is rather the same as travelling in a tumble dryer. It isn't pleasant, and whilst the sylph may not tire of taking it's passengers they quickly will. A sylph can travel 100km in a normal eight hour day, and those who wish to travel via sylph can normally stomach eight hours as long as they have the odd break here and there. Of course, the sylph never needs to stop, and so can travel 300km in a single day if it just travels with no breaks. So, travelling across Dragon Pass via Sylph could be achieved in little over a day. However, those who use this method are unable to sleep, and suffer five times the normal penalties. It is also impossible to finely manipulate objects whilst within a sylph, so eating is almost impossible.