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
Morse code abbreviations sentences and questions in short three character codes each beginning with the character Q. For example, the code word QTH means "My location is". If this code word is followed by a question mark as QTH? it means "What is your location?". Typically very few full words will be spelled out in Morse code conversations. Often vowels are left out to shorten transmissions and turn overs. Other examples, of internationally recognized usages of Morse code abbreviations and well known code numbers, such as those of the Phillips Code from past eras of telegraph technology, are usages such as WX for