It’s the airport equivalent of road rage: You race to your gate on a tight connection to see the door shut and your plane inching backward.

One reason gate agents are so strict about that closed door is an airline metric called “D-0” (D-zero), which designates a flight that departs at exactly the scheduled time. The industry-and government regulators-rigorously monitor this metric to see which carriers operate reliably and which don’t.

Aiming to alleviate at least some of this pain, United Airlines is testing a program called “Dynamic D-0” at its Denver hub to empower gate agents to delay a departure to accommodate customers and employees rushing to a connecting flight.

The system “tells an employee, tells customers, ‘Hey, here’s five or six customers that are coming to this connection; they’re going to be five minutes late, but we know we can make up the time in flight on this particular flight,'” United President Scott Kirby said Tuesday at an investor conference. “Sometimes we can’t, and we don’t hold the airplane.”