Anyone remember BASCO? Brothers' Air Service Company or something similar I believe. IIRC they operated DC-3s in parallel/competition with Aden Airways. Around September 1970 I flew in one of their aircraft from Khormaksar up to Taiz in Yemen Arab Republic (as was; Aden by this time was PDRY-Peoples' Democratic Republic of Yemen). I wasn't too thrilled at having to make the flight in the first place but my eyes were really opened when I saw all the wrecks littering the strip at Taiz.
After a few days in Taiz I flew up to Sana'a but I can no longer remember who with but I'm fairly certain it was in another DC-3. I remember seeing a YAR Air Force MiG-15 (I think possibly Russian- or Egyptian-flown) getting airborne at Sana'a - a real curvature-of-the-earth job. IIRC Sana'a is something like 7000' asl but on a plateau. Taiz is not quite as high but is in/surrounded by mountains. When I went back in the 80s the airline had become Alyemda (later still Yemenia) and the aircraft DHC-7s and Airbus 310s!