I think every two-, four-, six- and eight-engine airplane that carried--and flew on--a single test engine has so far been mentioned as a "world's heaviest single" candidate. Amusing, but irrelevant.

My own Top-10 list, culled from this thread and based on MTOW plus a "wingspan factor," is...

Boeing F-35
Republic F-105D
MiG-27
Lockheed U2
Tupolev Tu-91
Grumman AF Guardian
Tupolev Ant-25
Douglas Skyraider
Breguet Alize
Vickers Wellesley

Your mileage may vary, but that's my story and I'm stickin' to it.

Ladies and Gentlemen, boys and girls, "PPRuNe Threads" proudly present for your entertainment on page 3...weighing in at 20,600 lbs and with a wingspan of 88 ft...the "Big Bastard from Blackburn"...

The Mighty Cubaroo!

http://img153.imageshack.us/img153/1...baroo19241.jpg

http://img43.imageshack.us/img43/7260/71148289.jpg

Okay, you got me. Scratch the Wellesley from my list and substitute this monster. I love it!

Don't forget the Junkers Ju-52/1m, the original single-engine version of the Ju. With a span of 29m and length of 18,5m, it could dispute first place with either the Tupolev or the Cubaroo.

88ft wingspan, and the engine weighed a ton (according to Wikipedia) - amazing

Also increased the pilots' susceptibility to Decompression Sickness (DCS), as could MiG 25...