Gravitrons are newbloods who can manipulate gravity.
Gravitrons have been known to use their ability to increase or decrease gravity in an area to enable them to fly.
"Gravitons manipulate the bonds of gravity, utilizing the ability to both strengthen and weaken such ties. Gravitons have been known to "fly," after a fashion, or pin opponents to the ground." -Victoria Aveyard "War Storm" "On Silverblooded Abilities"