HA1 is probably a good idea for better utilization, but flights are not really a competition for this route. I have regularly seen both business executives and regular passengers preferring to go by mail 1A than a flight. (It was 'recommended' by the travel desk in our company for managers going to Madras for attending meetings).
For most people who need to reach Madras in the morning, taking the overnight train is a much more comfortable option than waking up at an ungodly hour and catching an early morning flight.
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more... Mail's rather patchy punctuality in the past few months may have resulted in making it a less preferable option, particularly for traveling executives who would have scheduled meetings.