The serials ZM135 to ZM200 are allocated to the Lockheed Lightning II (F35) and ZM400 to ZM424 have been allocated to the Airbus Atlas (A400M).
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See the site above for more info.
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the U.K. is currently using a system of 2 letters followed by 3 digits that began in 1940 with AA100. Certain letters are generally not used as they look too similar to others, and some letter combinations are not used for a variety of reasons. The numeric part of the serial was traditionally between 100 and 999, but in recent years they have started at 001 in order to get more use out of the current system. "Blackout Blocks" were incorporated into all serial batches in order to disguise the true quantities of aircraft ordered or in service, but this practice has now ceased, however serial numbers are being allocated to even more simulators, again this is to allow maintenance records on these high-tech training devices to be kept up-to-date.