The 737 has always had the nickname "the Guppy", especially at UA.

I will admit, without being privy to any sort of proprietary information, that a 747 on a 1600mi route didn't make a great deal of sense to me at first, especially with UA's 744 fleet beginning to get up there in hours on the airframes. It seemed to be motivated more out of necessity, since pre-merger UA only had heavy metal in Pacific, while CO had the flexibility of the GUM 737 base. That's not the first time I've been wrong about something... hell, not even the first time today!

I am excited about the possibility that UA may be starting to walk back some of its 'ramrod' post-merger changes, although there are plenty of other entirely plausible explanations for the return of a 747 on this route, beginning with cargo.