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How schedules are built

The flight on your ticket was planned in layers, starting years before you booked. Each layer narrows the choices: which cities, how often, at what times, with which aircraft, and finally which crew and which aircraft on the day.

From strategy to the day of the flight

1. 1 to 5 years aheadNetwork planWhich cities, which aircraft to order or lease
2. About a year aheadScheduleFrequencies and times, slots requested
3. Months aheadFleet assignmentWhich aircraft type flies each flight
4. Weeks to daysCrew and aircraftRosters for crews, and which aircraft (tail) flies what
5. On the dayOperations controlDelays, weather and swaps, in real time

Seasons

Airlines plan in two IATA seasons, which line up with the clock changes in Europe and North America. Slots at congested airports are allocated for each season, so the schedule is built around them.

WinterSummer: last Sunday in March to last Saturday in OctoberWinter

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Building the timetable

Planners decide how often to fly each route and at what times. Business travellers want early morning and evening flights; leisure flights can run at other times. Every flight must fit the slots the airline holds, airport curfews, the block time for the route and season, and turnaround times between flights.

Waves at a hub

A network airline times flights into its hub to arrive close together, then leave together after a connecting window: a wave or bank. More waves give more connections, but crowd the runways and gates at peak times.

Fleet, tails and crew

Next, each flight gets an aircraft type that fits its expected demand and range, and the aircraft are chained into rotations that keep them flying (high utilisation) while leaving time for maintenance. Closer to the day, each flight gets a specific aircraft, known by its registration or tail, and crews are rostered within strict duty-time rules. These are large optimisation problems, solved with specialised software.

On the day

Weather, delays and technical problems never follow the plan. The operations control centre swaps aircraft and crews, delays or cancels flights, and re-books passengers, trying to protect connections and get back to the plan as quickly as possible.

Season dates: One Mile at a Time; HungaroControl slot allocation.