Hi Andriyko,
Seatexpert.com gives some advice;
http://seatexpert.com/seatmap/65/Ame...(Three_class)/
as a BA gold holder you can use the LAX first class check in and have access to the Flagship lounge at LAX ( accessible through the Admirals club and you get a keycard to out in the slot by the sliding doors to access the FL.)
Regards
TBS