Closer to 2.5. Interesting but very dated, not so much in the facts themselves, but in how Serling has a clear agenda of defending the Lockheed L-188 Electra to the point that it seems rather biased. It hurts even more because it actually succeeds as a primary source, but the author's narrative almost puts what he has written into doubt with his peppered asides and "this author" moments sprinkled about.