The rule isn't 3.5 hours:
On flights over 2.5 hours that depart between 5 AM and 7:59 PM (excluding US Airways Express, US Airways Shuttle and transatlantic flights).
By contrast, Delta's rule is distance-based but 900+ mile flights will certainly be well over the OP's target of 1.5 hours.
251-899 Miles (1 to 2 hours)
Choose from a selection of complimentary snacks. Morning flights (departures 05:00-09:45) offer peanuts, pretzels, Biscoff cookies, biscotti, bananas, Otis Spunkmeyer muffins and Quaker Oats chewy granola bars. All other flights offer peanuts, pretzels, apples, Twix, Toblerone, Sun Chips and Walkers shortbread cookies.
900-1,499 Miles (about 2-3.5 hours)
A delicious meal will be served during meal times2, in addition to our snack selection.
More than 1,500 Miles (3.5 hours +)
A delicious meal will be served, in addition to our snack selection. On dinner flights, enjoy entrées from chef Michelle Bernstein.