Gas grill flames very high cooking chicked wings and vegetables
That's pretty typical for any sort of fatty meats -- as you cook them, the fat renders out, dripping into the flames below and igniting.

This is often referred to as 'flare ups', and some people recommend using a water bottle when grilling -- but don't do it, as this is actually a grease fire.

You'll typically want to move the food to another area until the flames die down, as there's not much else you can do unless you want your food to taste like a fire extinguisher.

You can take some preventative steps on a charcoal grill, by putting a container of water on the grate beneath the food being cooked (you'll be cooking using indirect heat), so that the grease drips into the water and doesn't flare up.