LINE SERVICE (to pay for Law school, already had my Private) - LRD 1976.
I was the Last Man to see a transient pilot depart in his nice MU-2 for the Factory Svc. center at San Angelo... see
Mitsubishi Heavy Industries America Inc.
@ the Fed-Man interview I stated the truth: He was clearly somewhat tired (age: 30's, maybe early 40s) after a long day, but IMHO fit to fly, no booze or obvious intox., familiar with his MeXican-registered plane 1 million %, and one of THE FEW Careful Ones that actually checked my replacement of his fuel caps. In the dark. I always liked to see that - I'd never made a mistake so far, but I surely will someday. Only ppl. that do real preflights are students and Pros. He struck me as a Real Pro - and I even made fresh coffee for him.
He filed IFR. After the pleasure of watching him preflight, I took my ladder back and, it being late, went into the ofc. where I heard him talking to ARTCC. They cleared him along right smart to 3000, then up to 5 or 7- I forget. He acknowledged crisply. But then he was seen to cleanly bust his assigned alt and just keep on climbing, as if in ATTITUDE HOLD mode. Many many ATC and other-AC relayed-calls, no answers. Ever.
They watched him go up to the AC's svc. ceiling, flail along steadily up there for quite a while... and then ... when the kerosene was gone... dive vertically into Kansas. Quite a ride, toured a few extra States but never enjoyed them, like Payne Stewart did in his Lear. So we pretty much knew the HOW = heart attack, anoxia, some pilot disability... but never the WHY.
I love everything that flies, but that aircraft is a
killer unless you have ALL the MOST 2008-2009 recent FAA Re-Cert, Re-Training Reqmt's nailed and re-nailed.
I can accept that- some ACs just aren't for part-timers. Like Ted Smith's Aerostars, etc. We had an orthodontist once that took ALL his ratings from my instructor one after the other in just a few Mo. - Private, Multi, Instrument... and we BEGGED him not to buy that fine Aerostar on our ramp "For Sale". BEGGED HIM! But what do WE know? He's a
DOKTAH 
and we're just.. pilots. So WITHIN THREE WEEKS he wound up strewing it, himself, and his wife all over the approach path to One-Three in Corpus. Lucky! THEY LIVED! In Full-body casts for 8+ mo. after leaving the Hosp. (chuckle) but...they were alive.
I think the MU-2 is a Flying Prostitute unless you are a HEAVY-RATED PRO. Wing Area = to a C-172's at THAT power loading and gross? NO ailerons... but Spoilers? Funky flaps that operate like NO other? Gimme a break ....
Rotate at 110, but if you lose one, no Vmc until 150? Sure, I'm gonna hold that designed-wimpy (un-needed!) rudder all the way over and take a 5-degree bank into my operative engine, until I realize that I am SPOILING THE LIFT on my Last Good Side.
And leaving my tire rubber on the far fence. Right-O! And do NOT forget all that fuel-weight waaay out on the wingtips that has its OWN ideas about Rolling Angular Momentum.
Yes, LOTS of simulator-time and MUCHO extra PRO-LEVEL training CAN solve this. But it's not and WILL NEVER BE a Non-Professional's airplane.
As they so murderously marketed it. 
I'm still troubled by one accident report: MU-2 shortie pinkie-diamond whatever was observed by other traffic to be "falling vertically in the level flight attitude" while
gently nodding its nose about 30 deg. up & down...up and down...all the way in.
I saw ONE MU-2 that I would have flown in. It had TWO nice guys up front with crisp starched white shirts and epaulets: 1 had 3 Stripes and the left-seater had 4.
PS: Oh yeah, I'm THIS guy:
YouTube - AMNESIA CRASHING