825 will run per day in July, and 850 per day in August; a time that usually sees 900 daily flights.
Portugal and Spain are said to be the destinations that will be worst affected.
Business Minister and MP for Sutton and Cheam, Paul Scully, wants people to be able to work more hours if they want.
Heathrow has already worked with airlines to limit passenger numbers at the busiest times of day.
Boss John Holland Kaye expects the aviation problems to continue for at least another year.