Each day, Delta operates an average of 260 flights at LaGuardia, an airport known for tight turnaround times, with roughly 25,000 customers and about 8,000 bags. The airline relies on a team of some 1,000 ramp agents, said Adam Ryan, a vice president for airport operations at the airline.

The handling process is intended to be swift. Across Delta’s operations, Mr. Ryan said, bag drop to loading should ideally take about 20 minutes.

By 12:46 p.m., two passengers and five checked bags were still missing. Five minutes later, all 60 checked bags were loaded and the plane, an Airbus A321, left its gate.