2 Flight Costing:
Actually one Il-86 has been lost near Moscow during ferry flight due to "MUCHO" style takeoff - they've set the stab trim too much nose up to make a show - then could not level off fast and lost the speed.....
About Yak-42 - I've got some experience with it 20 years ago.... IMHO one of the reasons could be the following:
1. Stab not in T/O range or
2. Flaps/slats not in T/O range (that's why they were running too long time, awaiting for proper setting) or
3. At least two engines problem. One engine lost can not lead to a crash with so low load (about 30% from max).