Thanks very much lamphs. Yes separate AA and EK tickets. No issue with 6-7 hours at the LO lounge. The only hiccup was that, although I had OLCI'd, EK didn't issue my boarding pass. So I had to pay the $70 walk-in fee which they refunded a few hours later after they verified my ticket with EK. Also had to talk my way onto the inter-terminal bus from T3 to T5.