Donkey duke,
Welcome to the party.
Couple of points to clarify first, although Hand Solo may have muddied the water just a little bit.
If Delta, CAL or NWA wish to PURCHASE slots once the open skies treaty is approved, they may. Of course, slots aren't exactly available at Woolworth's prices so they want some for free. (If one doesn't ask, one doesn't receive). Slots are also routinely "traded" among partners for seasonal and other reasons. Air France "could" lend some slots to Delta for the advancement of Skyteam, NWA "could" borrow some slots from KLM etc, post open skies.
If Delta wants to operate 11 round trips I believe they'll need 22 slots.
If CAL and NWA have the same wishlist, that becomes an additional 44 (total 66).
For all the competition you speak of remember AA and United BOUGHT the rights, on the open market, to fly to Heathrow (AA from TWA and UAL's as part of their Pan Am purchase-which Delta COULD have matched if they'd wanted to at the time).
If anyone thinks that the Gatwick Express is intolerable, they've obviously NOT ridden the Piccadilly line at rush hour or sat in a black cab for an hour and paid $100 for the "guess who I just 'ad in my cab" pleasure!
The real irony here is that AA is more than likely going to transfer most of its US/UK flying to BA.
Here in the US, LGA (La Guardia,NY) became a complete cluster because too many airlines felt the compelling need to use this "convenient" airport. What the airlines didn't foresee was the typical one hour ground hold incurred on a regular basis because the world and his dog showed up and literally jammed the pavement. What the passengers didn't expect was the opportunity to stare longingly out of the window at Manhattan for the usual 60 minutes when, if they'd gone to JFK (NOT capacity constrained) they'd probably already be in their office etc. LGA is a 15/20 minute cab ride, JFK's about 35 mins to midtown.
The real problem though was that although EVERY AIRLINE wished to pare down its operation at LGA NOBODY wanted to be the first. Hence, when the Port Authority finally held a meeting among all the airlines and said "this is crazy, we're going to go back to our previous slot allocations" they received a round of applause and the airlines collectively sighed in relief.
The same thing will happen at Heathrow.
One can't plan a schedule, and optimise aircraft use, AND pad the schedule effeciently.
If one assumes NWA,CAL or DAL allocates one aircraft for the daily roundtrip (i.e. in a 24 hour period this aircraft flies to the UK and returns , is cleaned and serviced in between and then repats the trip) when the total cycle creeps up OVER 24 hours "part" of an additional 1/24th aircraft comes in to the mix for each hour.
When the ground jam results in this requiring 1.5 aircraft available in order to cover the service, the planners start looking at their other options. In Delta's case they could choose to fly to Paris and connect pax more effeciently on an AF hop to London. Same for NWA,CAL. Fly to Amsterdam and KLM it to London. Oh wait a minute, they already do that!
Heathrow will become another LGA for DAL, CAL and NWA.
Here's an opportunity for DAL, CAL and NWA to push for "ownership" of Gatwick and build a little fortress there. There are multiple selling points for Gatwick as an O&D (origination and destination). I think they're so blinkered by LHR that they're collectively missing a golden opportunity.