Just a quick rebuttal to economyman's suggestion that you can book and change... this was not at all what I found, and it really made my life more difficult when I tried to follow that advice.

I booked ITM-HND on JL in the early afternoon hoping to switch to a flight five hours later (these flights leave every hour). Not only did the later flight not pop up — it tried to charge me a change fee.

A phone call to BA solved my problems, as they changed me to the later flight for free because it was less than 24 hours. BUT at first she couldn't find the later flight just as I could not.

Later when I got to ITM the JL agent tried to charge me a change fee for having changed. I pushed back.

Bottom line: if you don't see your flight, just call.