There are two factors that play into gaining a 180 degree split leap or jump once you have acquired the flexibility.
One factor is power on the jump. If you develop enough jumping power from your legs and back then you can jump so hard and fast that the sheer momentum throws your legs up to a 180 degree split and beyond. Conditioning exercises are in order if you wish to go this route.
The other factor that comes into play is contraction strength or ability of the agonist muscles to shorten. These are the opposite muscles that are not being stretched. Unless you can contract, tighten, and shorten those muscles on the other side to physically pull your legs into a 180 degree split in the air then your only chance is to rely on momentum.
Sit on the floor in a straddle. Put your hands flat on the floor in front. Keep your hands touching the floor and lift your straddled straight legs and feet up as high as you can off the floor while you remain seated. This is contraction strength or contraction ability.
A variation is put your elbows down along with your hands and lift your legs, remain seated. Or do it in a jap split. Or do it piked legs together. The more contraction ability you have the better and higher you will be able to lift your legs in the air.
For the back leg get in a normal front split and lift the back leg up off the floor. Or do it standing up holding your foot behind you above a high beam without allowing your back leg or back foot to touch or rest on the beam.
There are many ways to work contraction strength of agonist muscles. Once you get the idea then you can create your own set of exercises that suit your tastes. The best result is to be able to use both superior jumping power and superior contraction strength combined with flexibility to accomplish a quintessential split leap.
