When a pilot pulls back on the controls too quickly or carries too much speed into the flare, the aircraft generates a sudden spike in lift. Instead of settling smoothly onto the runway, the plane climbs back into the air. This forces the pilot to either hold the pitch and wait for the speed to bleed off, or execute a go-around to avoid a hard landing.
Heard on the job
He carried ten extra knots over the threshold and ballooned when he chopped the power.
Insider tip
If you balloon significantly, the safest response is usually to apply full power and go around rather than trying to force the plane down.