No Fly Tipping . . . . .

On the fly meand to move or do something in a hurry. so tipping on the fly, so you don’t get caught.

a. To move with great speed; rush or dart: The children flew down the hall. Rumors were flying during their absence.
b. To flee; escape.
c. To hasten; spring: flew to her students’ defense.
5. To pass by swiftly: a vacation flying by; youth that is soon flown.
6. To be dissipated; vanish: Their small inheritance was quickly flown.