This is double the number of slots that competition authorities in Washington and Brussels have said should be relinquished and four times the number that the Office of Fair Trading says BA and American should be required to give up.
The tough line being taken by Delta, the biggest airline in the world based on passengers carried, is designed to put extra pressure on regulatory authorities on both sides of the Atlantic as the deadline looms for a final decision on the long-delayed alliance.
The OFT recommended that BA and American relinquish 168 take off and landing slots at Heathrow a week as the condition for allowing the alliance to proceed. The European Competition Commissioner, Karel Van Miert and the US General Office of Accounting, which reports to Congress, both recommended that 350 slots be surrendered.
But Delta said yesterday that between 700 and 800 slots should be given up and redistributed to rival carriers if real competition were to be preserved following the launch of the alliance.
Approval for the BA-American tie up will pave the way for an open skies agreement between London and Washington, liberalising air services across the Atlantic by permitting any US carrier into Heathrow.
Stephan Egli, Delta's newly appointed vice-president for the Atlantic and Pacific, said that releasing 168 slots would only allow proper competition to take place on one route - Heathrow to New York's JFK airport - where the combination of BA and American would otherwise dominate with 13 non- stop flight a day.
Mr Egli said that if there were to be real competition on the four, or give other routes where BA and American would have a stranglehold, then as many as 800 slots would need to be freed up: "We recognise that is a tremendous number of slots but it needs to be done if we are not to allow a monopoly."
The alternative, he added, would be higher price and less choice because other carriers would simply drop out of the routes as they would not be able to compete on equal terms.
A BA spokesman said of Delta's demand: "There are some absurd suggestions out there but this one takes the biscuit. All our competitors have rallied against the alliance because they have their own agendas to pursue."
The BA team working on the alliance planning meets today to take stock of the situation and continue preparing the airline's formal response to Mr Van Miert. Bob Ayling has set an effective deadline of November for approval for the alliance otherwise the two carriers will not be able to plan their summer schedule properly. The bi-annual slot scheduling conference, attended by all the world's airlines, takes place in Brisbane, Australia, between 13-20 November to allocate slots for all airports for next summer.
Even if approval is finally granted it will have taken BA and American two years from the date of their original announcement to get the alliance airborne.