Summer or winter: why, for airlines, half seasons don't exist

Summer and winter. In the world of airlines there are no half seasons.

Spring and autumn do not exist, tomorrow Sunday, March 31, for example, begins the summer season, 'summer' as they say, although according to the calendar, spring has only been starting for about ten days.

In fact, the two seasons coincide with the so-called 'time change' in most countries of the world. Thus, The 2024-2025 'winter' will start on Sunday, Oct. 27, when daylight saving time ends And we will turn the hands of the clock back one hour.

The start dates of 'summer' and the beginning of 'winter' also coincide with The startup, or stop (or upgrade or downgrade) of many seasonal connections or with machine changes in the sense of more or less capacious and more or less state-of-the-art aircraft.

To give an example, some of the routes between Italy and the United States undergo a downgrade as to aircraft used in the 'winter', which is the 'dry' season (except for the Christmas vacations) in that market. Always between the United States and Italy there are also routes that experience a reduction in weekly frequencies and others that, with the arrival of 'winter' are discontinued and then resume with the start of the next 'summer'.

Of course, this all happens in principle, in the sense that there are seasonal routes that are started much later than the end of March, with the arrival of summer proper, and perhaps are terminated in late August or late September.

The existence of only two seasons, however, is not only related to the change of time from solar to summer time and vice versa, nor when the warm season or cold months arrive. Instead, and more importantly, it has to do with the slot allocation procedure at many airports performed by Iata (International Air Transportation Association), the body that brings together some 320 airlines in 130 countries that carry nearly 85% of passengers.

Well, Iata meets twice a year for the purpose of examining the distribution and use of slots at the world's busiest airports, those so-called of 'Level 3' or 'Slot coordinated': in all, more than 200 airports through which more than 40% of the world's passenger traffic transits. Included in this list are such airports as. London Heathrow, New York JFK, Dubai International, Tokyo Haneda, just to name the most important ones.

In the two annual sessions la Iata analyzes slot utilization at these airports., checks whether any are available and proceeds, in agreement with its member companies, to confirm or reassign them or to bring in new companies if there are vacant 'spaces'.

Ed it is following this procedure that companies 'build' their schedules twice a year, for 'summer' and 'winter'.

• iata