Fly.
The word aerial has three syllables like so: aer-i-al.
Trestle is a word for railroad bridge.
UFO is not a word. It is a TLA (three-letter-acronym) for the three-word-phrase "Unidentified Flying Object".
Ballast
One seven letter word, One two letter word and a five letter word, One three letter word and a four letter word, One three letter word and two two letter words, Two three letter words, Three two letter words, A two letter word and a four letter word, A six letter word, A two letter word and a three letter word, A five letter word, Two two letter words, A four letter word, A three letter word, or A two letter word.
I've is a three letter word. I'll is another three letter word.
Hihi Irirangi is the maori word for 'aerial'.
Imp is a three-letter word for rapscallion.
A three letter word for help is aid.
A three letter word for a summit = Top.
A three letter word for gender is sex.
A three letter word for debt is owe.