The post-COVID era shows the widest seasonal swing and is the only one whose quietest quarter is the first. The extra width comes from its first year alone; without it the swing is half as wide and no longer the widest.
What this shows: The chart plots Pre-deregulation (1984–89), Post-deregulation (1991–00), Low-cost carrier era (2004–19) and Post-COVID (2022–25) on a vertical axis of Share of era mean (%).
Conditions and method
The gap between the highest and lowest quarter is 17.8 points of the era mean in the post-COVID era (2022 to 2025) and 8.9 points without its first year, 2022. The widest gap in an earlier era is 13.3 points, in the era labelled Post-deregulation (1991–00). The wider swing comes from 2022 alone.