Focus of my question is given in the title.
More generally, which movement options a prone creature has? I am aware of the 5-ft. crawl and the stand up (both move actions that provoke an attack of opportunity).
Example given to further clarify.
A gargolye standing on the ground has been tripped (thus falling prone). On his subsequent turn may he use his fly speed to move away and gain altitude directly from the prone condition? Must he stand up before taking flight?
As far as I know, there is no explicit rule on this exact issue within the 3.5 core rules.
How exactly a Prone creature's land movement is hampered is not even defined. Using a legalistic definition, I can not see anything that, say, prevents Running while Prone, nor anything about a Prone creature needing to (or being able to) crawl. As far as I can tell, people just assume this due to the names of the conditions (and rightly so, in my opinion). There's a limit to how defined we can demand the 3.5 rules to be.
However...
Here's what I can infer on the subject of Prone creatures flying.
I'd say no, a creature that has the ability to fly but has been tripped can not fly away without first standing up.
This is because the following is a part of the description of a character being Prone: "The character is on the ground". I'd argue that a character that is "on the ground" can not make use of special options relating to flight.
However, it is not so easy getting a creature that can fly to be Prone to begin with, as Tripping has a special effect on flyers rather than rendering them Prone. See page 145 of the Rules Compendium:
Tripping a Flying Defender
A winged creature can be tripped, and if it is, it falls as if it didn't maintain its minimum forward speed.
As for whether Prone creatures have special uses for their move action other than crawling and standing up - no. Once again, nothing is defined.
No, it must surely first use a move action to stand up (thus provoking attacks of opportunity) and then try to fly away by using his remaining standar action as a move (actually fly) action. The only restriction I see to exist is that a creature with a flying manuverability of Average or worse, must still fly his "Between down and up" flying distance before flying away. Check this: http://www.d20srd.org/srd/movement.htm
There was a similar question here, the conclusion of which is:
Page 52 of the Faq explaines that its possible to trip a flying creature and that the result of succsessfully tripping said airborne target is that they stall.
After some research into flying, and some movement, it seems that flying creatures do not go prone. But these rules always assume the creature which is "flying" is currently flying.
I suppose if a creature (or character) is already prone and wants to initiate flight then it would need to first get up, depending on if it has wings or not.
Having wings which grant flight requires a move action, as flight is the method of movement, and prone characters can only crawl or get up for their movement action.
Magical flight is different than physical flight because it is a free action. And so can be performed while prone. This might still provoke an attack of opportunity.
