On Monday, April 7, 2014 8:09:06 PM UTC-7, JS wrote:
The sixth of April has over 800 flights posted.

Jim

From a quick skim, the answer is:

2859 flights posted
Sunday, May 13, 2012

The largest number of flights, the total for the peak day, in any given year has not varied by more than 10% since 2008. It is usually a weekend day in May, but one year it was in June and one year in July.

Bruce SL