Was listening to an interview with Will Shortsz, the bane of many a crossword puzzle solver and he said one of his favourite clues is:
A great tower (3 letters)
I'll let you know when someone answers correctly or next week so as not to spoil the fun.
The C47 is a military transport plane used for towing other aircraft. There are other air transporters of even shorter names, though some of which may not be considered 'tower.'
Good try but you don't usually get numbers in crossword puzzle answers, but you're on the right line of thought.
So as not to give it away all at once in case I've got it: just because the clue specifies 3 letters doesn't necessarily mean they're three different letters, right?
I didn't listen to that interview, so my first take was a 3-letter word for a "great edifice" like maybe the WTC.
Reading the responses in this thread, it now seems clear that Shortsz used a long "O" when he gave his clue. So that explains where Ron is going, but also leaves possibilities like "GMC," "RAM," and for that matter "ass."
And nelgin, yes, numbers in crossword puzzle aren't common, but I've seen them used on occasion. And isn't Sudoku essentially just a number crossword puzzle?