Is there any specific reason as to why airline schedules for the summer season start around 27 March and winter season around 27 October? Thanks.
The main reason for new schedules in March and October is the Daylight Savings Time changeover.
It is a MAJOR headache for airlines all over the world. Schedules have to undergo extensive restructuring during the switch over from summer daylight savings time to winter standard time. Maintaining code-share connection times is the biggest priority.
What makes this all very difficult is the fact that many countries and localities do not observe daylight savings time, or have different dates for the switch-over. This is especially true for flights between northern and southern hemispheres.
During Nov-Mar, snow is common in Europe and the continental US, which means (a) more schedule padding to account for airport delays and deicing, and (b) passengers wanting to fly to ski destinations.
During Apr-Oct, snow is unusual in Europe and the continental US, which means (a) less schedule padding due to good weather, and (b) passengers wanting to fly to beach destinations.
Airlines flying in other regions probably have different scheduling periods to account for different weather trends, e.g. summer/winter reversal in the southern hemisphere, monsoons near the equator, etc.