I've recently started an Elysian Drop Troopers army, which features of number of flyers. Just in time for Warhammer 40k 6th edition!
Each flyer is unique, featuring variant colour schemes and individualised pin-up nose art. Thare are 6 flyers in the army, including a Vulture Gunship and a Thunderbolt.
These pictures show some of my weathering techniques, especially on the engines and weapon mounts.
Here are some highlights of the two Valkyries and two Vendettas...