Back in the early 1950s, an RAF aircraft went missing and there was an appeal on the Home Service (Radio 4 today!) as it then was for radio amateurs to listen for it. I don't think anyone heard anything, but there was certainly a procedure in place where by 'if all else failed' they could call in an amateur band. A friend who is licenced ended hi RAF days in the driver's seat recounts how in a Varsity flying over Italy - presumably on his way to somewhere like Cyprus - in the early 1960s they had a power failure and he went down the back and fired up the T1154 and R1155 and called Speedbird control (BOAC in those days)in London to pass messages. Another amateur - long dead now - was an airborne 'WOP' in the mid to late 1940s and in a Dakota, flying in the Far East had the main tx fail. Using the low power Command tx he called on Morse and explained 'Main tx u/s'. Now a Command transmitters (SCR 274series) were a low power short range HF equipment and Morse transmission was every much an afterthought and they could not be keyed at any speed above about 12 words per minute. So Martin's message that 'Main tx u/s' should not have been copied as it was as 'Main tanks u/s' which triggered a major SAR operation. As one can imagine, when the Dak arrived at its destination and on time, the brown stuff flew around!.