Why is it scary? Engines are a significant part of airplane cost and just like planes they only make money when flying, so it totally makes sense to use working engines from grounded aircraft as a replacement for flying aircraft. All airlines do this all the time.
I think it's more like this: If they stopped making payments, it's safe to say they might be cutting corners in maintenance as well.
"We just watched and waited until the crew checked into their hotel", Popovich says, "then we grabbed their plane and flew away."
That certainly doesn't sound like they're doing a lot of inspection to ensure a safe return. Granted, it's only their hind-ends and they are aware of the risks, but I think this guy and his crew certainly deserve a brass balls award.
That's one of the beauties of a turbine engine. If it starts and N1, N2 RPM and fuel flow is within spec, and you don't exhaust the fuel, the chance that that engine will run for another 5 hours is extremely high.
If my experiences with my own (single piston engined) airplane are in any way representative, I would be surprised if the first flight out of major maintenance isn't statistically significantly riskier than a random repo flight.
