There is only one file type that uses the .LTR extension:
An LTR file is a letter file used by various document authoring programs such as IBM Lotus Forms. It contains a message or other type of correspondence. LTR files are stored in plain text, which means they can be opened by any text editor.
You most likely will never come across an LTR file because the majority of programs that created the file have been discontinued. However, if you do find an LTR file you can open it with any text editor.
|Any text editor|
Updated: January 19, 2017