Here's a list of unsafe airlines (pdf). Openskies is not on there.

Of the "safe" airlines, I know one that decided to divert and land in Damascus in the middle of the Syrian civil war, apparently because they didn't have a fuelling agreement in Cyprus.

Another "safe" airline I know forgot to "close the bonnet" on one of it's planes, which required 2 seperate people to cock up.

The same "safe" airline had a pilot drive a 747 into a building.

Openskies is not one of those airlines, nor is it on the banned list.

All airlines operating in the EU and US (even Air France) are safe. Personally I wouldn't fly Air France after than Damascus incident, but intellectuality I know it is unlikely to happen again.