When is a horse ready to learn flying lead changes?

A horse is ready to learn flying lead changes when it demonstrates a specific set of foundational responses consistently and without anxiety — and that standard, honestly applied, delays many horses from lead change work longer than their riders would prefer. The prerequisites are not arbitrary; each one directly supports the mechanics and balance that a clean, straight flying change requires. The horse should be able to lope collected on a loose rein without falling on the forehand or rushing, because the collected lope is the physical position from which a clean change is easiest to produce. It should counter-canter willingly in both directions for at least a full circle without swapping leads, because counter-canter proves the horse can maintain a lead through balance and rider direction rather than defaulting to the comfortable lead for the direction of travel. It should move its shoulders and hips independently from leg cues at the lope, because the flying change requires the rider to shift the horse's balance and hindquarter position with a leg aid at the exact moment of the change. It should stay straight on a straight line without drifting, because a horse that cannot travel straight will not change straight. It should change its bend from one direction to the other without anxiety or resistance, because the lead change asks the horse to reorganize its entire body from one bend to the other in a single stride. A horse that is unbalanced, rushing, reactive to leg aids, or unable to counter-canter is not ready for flying changes regardless of its age or training timeline, and installing the change before those prerequisites are solid produces a change that is crooked, late, or anxiety-driven from the beginning.