As a very general rule, flights via any airline between airports that most people travel between are extremely unlikely to result in a fatality. If you count safety as being "walking off the plane alive" then most airlines are "safe enough".
ie The chances of dying on a low class airline's flight on an other than backblocks route is minimal - and even the very best airlines have disasters occasionally.
In AirlineRatings.com's table of airlines (see below) about 90% of the about 300 airlines listed had not experienced a fatality in the last 10 years.
AirlineRatings.com - Safety and service ratings for many airlines.
Comparison table for all airlines ratings.
The table also rates "product" out of 7 - I've not listed those (Air Koryo 2.5/7 for "product")
Safety score out of 7 :
Aeroflot scores 7 / 7 for safety.
Air Koryo scores 5.5
Ryan Air scores 5.0 (how I don't know)
Nepal airlines score 1.
7.0 Cayman airways
5.5 Air Koryo
5.0 Air Botswana
5.0 Cape Air
Personal experience: I have travelled reasonably extensively in China in recent years. I have never been 'scared' of flying in the classic sense but had always had an awareness of the "all or nothing" aspect of air travel and the fact that bad things sometimes happen. A few years ago I planned to travel diagonally across much of China from the south East near the coast to near top left (North West) (Urumqi in Xinjiang) - about a 7 hour journey as I recall. I researched the records of all the Chinese internal airlines - and found them to be often a fairly 'easy going' lot safety wise by western standards. I found many reports of below standard maintenance, practices that ware less than ideal and a general approach to safety which was not absolutely terrible but which also was not first class. And I also found that most of the airlines had lost one aircraft in the decade pre 2000, none had lost one post 2000 (as of about 2009). The only Chinese airline that had a worse absolute fatality record was Air China - the Taiwanese national carrier with 3 losses over a near 20 year period.
I've since found that, quite unconsciously and unintentionally, my attitude to air flight has relaxed to the near blase level and I have to actually remind myself that making my peace as appropriate preflight is still probably a good idea. ie I'm not too concerned on any given flight.
In India in 2014 I flew Spice Jet (4/7 for safety),
I've flown Ryan Air (3.5/7)
and I want to visit Nepal but am not keen about Nepal Airline's 1/7!