SQ
So, we now have SQ code sharing to 8 USA domestic destinations beyond IAH operated by UA, and on Flybe's extensive network beyond MAN.
So the bit in the middle we are missing is a UA codeshare on SQ's SIN-MAN-IAH service. According to an article published in Aviation Week yesterday that could soon be fixed, as it states that SQ/UA have applied to the US DoT for the approval of blanket code share rights on all Singapore/USA services operated by either carrier, including via intermediate points. Unfortunately I can't post the link.