Rolland. These were the transport routes by contracted civilian airlines pre-the Lend-Lease act of March 11 1941; crews would come from PanAm, BOAC, ATC (US), and RAF Ferry Command.
The map below is routes as per June 30 1942, as you say they still skirted Arabia on to Iran or India. Apart from the politics it would be better to come down there rather than in the middle of the Arabian desert. Terminus was Chungking or Kunming in W. China. I think the "Horseshoe" route was originally round Africa to avoid the Mediterranean ?
Incidentally crews had blood tests before leaving Takoradi in case of illness on route.
http://www.ibiblio.org/hyperwar/AAF/I/maps/AAF-I-11.jpg
Nick