An aircraft earns nothing while it sits at a gate, so the interval between arrival and next departure is planned tightly. That interval, rather than flying time, sets the shape of a short-haul timetable.
The ground interval is a sequence, not a pause
A turnaround is a chain of tasks in a fixed order: passengers off, cabin cleaned, catering swapped, holds emptied and refilled, fuel taken on. Some steps overlap, but several cannot start until an earlier one finishes.
The total time is therefore set by the longest chain of dependent tasks, usually boarding or refuelling. Trimming a task that is not on that chain changes the departure time not at all.
Airlines spend their money on the slow step for that reason. Aircraft boarded through two doors, or stands with a second jet bridge, exist to shorten the queue rather than to improve comfort.
Short-haul economics push the interval down
A single-aisle jet can fly several sectors between morning and night, and each extra sector spreads the aircraft's fixed daily cost across more paying seats. Cutting ground time is what makes another sector fit.
This is why low-cost carriers guard the turnaround so closely. Their fares assume a high number of flying hours per aircraft per day, and only a short, repeatable ground interval delivers that.
Full-service airlines accept longer intervals because they carry connecting passengers. Transfer bags have to be found and reloaded, and late connections have to be waited for, neither of which compresses well.
Delay travels down the aircraft's day
Because the same airframe flies four or five sectors, a delay in the first one is inherited by every later flight unless something absorbs it. The aircraft cannot leave before it arrives.
Crews follow the aircraft on some rotations and swap on others, so a late inbound can also strand a crew at the wrong airport. The recovery cost then exceeds the original delay considerably.
Airlines protect against this by concentrating slack in specific places rather than spreading it thinly. One longer sit in the middle of the day can reset an entire rotation.
Slots and duty rules put hard edges on the plan
At busy airports, departures are governed by allocated slots that cannot simply be pushed back an hour. Missing one means waiting for the next gap in a sequence that is already full.
Crew duty limits impose a second hard edge. A rotation that overruns can reach a point where the crew legally cannot operate the final sector, cancelling it outright rather than delaying it.
Both constraints reward schedules that are conservative early in the day. A timetable built with no margin looks efficient on paper and collapses on the first morning of bad weather.
Padding is deliberate and it is measurable
Published block times are longer than the flying time an aircraft actually needs, and the difference is intentional. It covers taxi queues, holding, and the ordinary friction of a busy airport.
The padding is why a flight that leaves twenty minutes late can still arrive early. Airlines are judged on arrival punctuality, so the buffer sits where it protects the reported figure.
Passengers feel this as flights that seem slower than they used to be on the same route. The aircraft has not slowed down; the schedule has absorbed the congestion around it.