Flight attendants beware! Fasten is often mispronounced, because the spelling is deceptive. The t is not pronounced. In fact, all t‘s preceded by an s and followed by -en or -le at the end of the word or unit are silent:
Words derived from any of the above behave in the same way, i.e., the t is also silent in whistling, bustling, hustler, rustler, etc.
The t is also silent in Christmas (KRISS-mus), in soften (SOFF-un) and (sometimes) in often (OFF-un).
©2013 Baxter Publishing, Hilversum, The Netherlands