I have been a bit slow off the mark and did not realise that I could select and reserve my flight seats on American Airlines website. The best ones have gone but I have managed to get aisle seats on both inward and outward London-Dallas flights. I am not bothered about the connecting flight as it is only a few hours long and, by not booking seats now, stand a good chance of getting one of the better seats currently requiring a £69 premium. To get this service you need to sign up with both Checkmytrip.com and AAAdvantage.com. I wish I'd known sooner but at least I can now check in online - another good reason to sign up to these two sites.