Morse code was later made the standard by the International Telecommunication Union (ITU). Morse's original code specification, largely limited to use in the United States and Canada, became known as American Morse code or "railroad code". American Morse code is now seldom used except in historical re-enactments. In aviation, pilots use radio navigation aids. To ensure that the stations the pilots are using are serviceable, the stations transmit a set of identification letters (usually a two-to-five-letter version of the station name) in Morse code. Station identification letters are shown on air navigation charts. For example, the VOR-DME based at Vilo Acuña Airport
American Morse code 1851. It was necessary to have a common code as the Union had also agreed to direct connection of cables across borders (as opposed to recoding and retransmission by an operator). The code was adopted as the European standard in 1865, and was known at first as "Continental Morse," although as its use spread it also became known as "International Morse." At this point the original Morse Code started to be called American Morse, to differentiate between the two main standards. There was some resistance to adopting International Morse in the US. This resulted in international Morse operators in the