We might easily underestimate the ZEUS steam driven SRP, but even today (more than 50 years after its introduction) NATO planes do not fly below 3000m, to avoid the Strela-Shilka pair.
Hpasp Free SAM Simulator, "Realistic to the Switch" (U-2 over Sverdlovsk, B-52's over Hanoi, F-4 Phantoms over the Sinai, F-16's and the F-117A Stealth bomber over the Balkans.) http://sites.google.com/site/samsimulator1972/home
