United Airlines' fleet of 777-200ER's (which is I believe, 38 strong) is currently rated to a MTOW of 648,000 lbs, as opposed to a max for the 772ER of 656,000lbs. This limits their range (so as to be shorter than that of their 744s). I'm wondering why UA ordered their 772ER's with this lower MTOW, and why they don't have it paper increased to 656,000? They are powered by Pratt and Whitney PW4090s, which aren't the most powerful variant on the 772ER, but could I believe support the 656,000 MTOW. Moreover, with its full range, the 772ER would be able to fly routes for UA more effectively than the 744 does.
The 772ER could bolster australia routes in summer, fly routes like IAD-KWI (as it has better cargo, fewer seats), as well as a number of other flights.
Anyone have any idea why my favorite airline doesn't have its 772ER's rated for full MTOW and full range? I enjoy their 772ER's much more than their 744s (if you've ridden their 744s, you understand).. and I'd love to see the 772ER fleet better used.