The most impressive I have seen was in Gibraltar, the line was a considerable distance from the office and we needed some Nitrogen bottles, not having any radios I walked over to the FRA guys who were on the next pan with a Hunter, nope we haven't got any either, but not a problem, he walks out to the side of the aircraft, and starts waving his arms about, distant office door opens. out comes a chap, waves his arms about too and the guy I was chatting then comes back and says the bottles are on their way... damned handy this semaphore lark, he says wiith a grin.