Jag har löst det med denna SQL fråga:
select stats.flight, stats.date, max(stats.kgs), stats.awb from stats,
(select flight as test1 from capacity where date='01JUL' and route='GLA LHR') as test2
where test1=stats.flight AND stats.date='01JUL' group by stats.awb, stats.date, stats.flight
order by stats.flight, stats.date, stats.awb