Connecting within 24 hours without a through ticket / with two separate tickets (as indicated above by
teemuflyer ^, and verified by my experience today - and previously, but today I took the time to pay attention to the process, as the EXP agent didn't know what the heck I was talking about):
We are connecting at LHR on a (return legs) KEF-LHR-ORD-SFO FI to AA, separate tickets, but (barely) with 24 hour connection. Contacting AA, we were able to give the FI (Icelander) ticket number - this allowed the Rate Desk to view the FI (1008-) ticket, and delete the APD from our (001) AA ticket, resulting in a cost savings $452.40 for two people.
This took some time - over thirty minutes for the EXP agent to get the Rate Desk to research it, view our FI tickets and make the requisite changes to our tickets. Interestingly, the otherwise capable EXP agent did not know this could be done; he thanked me for the opportunity to learn something new. I smiled all the way to the bank.
Off topic, as one ticket was a paid ticket and the other an award ticket, asking the agent to associate the two PNRs with a "TCP" (To Complete Party) took little time and easily got it done. When I went to get the paid ticket at the local airport ticket counter (I was using a voucher for partial payment) the longtime Ticket Agent (ex-TW, iirc) knew how to accept and document the voucher, but did not know about the "TCP" annotation in the remarks section of the PNR.
Knowing all this stuff from FlyerTalk is, as they say in New Orleans, a nice
lagniappe (in southern Cuba it's "
la ñapa" - what you possibly
didn't know is the term is from the Andean Kechwa / Quechua / Runasimi language). FT ^!