Looks like BAC (Boeing Airplane Co.) is buying up retired UAL 757's & 737's and some retired BA 737's to turn into freighters, as the address of Box 2707 is Boeings main mail address.
I know that Fed Ex is buying Wichita converted 757's ( I've seen a couple and they do look really cool) as the supply of 727's with reasonable hours left is dwindling. That's really ironic (and darned smart) as Fed Ex refused to purchase brand new 757-PF's when the '57 line got started because they couldn't justify $42 M for a '27 replacement and did their own engineering/conversions on a bunch of retired 727-200 pax aircraft, but now that older 757's are being converted by BAC into box haulers-and come with a Boeing approved conversion it makes good business sense.
Several package outfits including a really big one that uses very dark Brown paint discovered, if you buy a converted passenger 727 with a big door, any repair you submit to Boeing engineering comes back as a repair for a passenger 727, not a freighter because Boeing built it and approved it as a passenger airframe (@ BFG we discovered that the outfit who modified those Brown 727-200's mislocated the cargo door one frame, 20 inches, too far aft which solves the issue of why getting a K loader up to one was so difficult). 727-100QC's were different because they were built new as freighter/passenger convertable, as were the very last (17 total) 727-200's built for Fed-Ex as 727-200F's.
So it looks like Boeing is getting ready to convert a bunch of airframes in the near-ish future to be ready when the airfreight business picks up again.
