Not sure how much cargo shifts between Brum and Detroit these days, rewind 10-15 years it was enough to fill an MD11 a week but that was when Ford engines were put in Jags. Assuming it's auto industry related freight than India, China and Saudi Arabia would be the obvious choices. With Saudi already covered, China ruled out and India served from Brum I'm a little stumped unless it's a new carrier to India or the flights from Brum are already full with cargo?