IIRC, TWA sold the LHR slots to AA as they gradually went downhill. TWA had a lot of 747SP, 747-100, and L1011. I used to fly the 747 to LGW and HNL. I think the L1011 was for Frankfurt and CDG but not certain.

When AA bought TWA, the plan was to have a second Midwest hub in STL because the previous two summers had been a disaster at ORD. There were several domestic mainline connections available in STL. Then, as it continued to bleed, they switched to an ERJ hub. It continued to be a diverse group of cities covered including cities ranging from Seattle to Hartford. STL was always a legal connection under fare rules and I would connect through there because the AC was great, connections were easy, and memories., It was bizarre to see a huge hub that was largely vacant.

At some point, Chicago realized it that AA having a nearby hub was a potential problem and built the new runway. In the meantime, WN had decided there were a lot of disaffected former TW/AA loyalists and decided to take over STL.

Then the tornado hit. Strange that it only hit the former TWA side and spared WN. It did, however, deal with all the empty gates and save the airport a lot of money.