Ski jumps

During the downhill ski racing event, skiers usually have to take a jump[???]: they are in the air for a while.

Questions:

• How can you recognize a jump from a course profile/cross section?
• Does the speed of the skier matter? That is, do you have to be going a certain speed to become airborne without pushing yourself off vertically?
• Is it faster to fly through the air, or to stay on the snow?
• What about snowboard jumps?
• What about skateboard jumps?
• The ski jumping event?