I know both US and PI used the 733s for transcon. At Piedmont, we had 4 different A/C types doing the transcon runs. Initially just the 727, then the 733, followed by the 767 once they arrived on the property and, finally, the 734. Man, we had some SWEET trips on the 767 back in the day....4 day trips with one transcon leg per day. Ahhh. But I digress. I can tell you the 733 and the 734 were miserable planes to be on during transcon flights, either as a PAX or as a F/A. I recall the 734 didn't last long on those runs and I think you're right, they just didn't have the range. I don't remember the 733 ever having a problem with it, but I DO remember having to make unscheduled landings for fuel a couple of times on the 727 on westbound transcons due to headwinds. No doubt the 737NGs truly are a whole different breed of A/C and that's a good thing for anyone who's on them transcon. If you told me I'd ever have to work (or ride) on a 733 for 5 hours across the country again, I'd probably just take Greyhound instead! 😛