This is kind of the same that Gymnotide posted, apart from that Gym didn't post a working strategy T_T
If the trick is to beat Salamence, then Flygon could use the simple strategy every single pokemon knows: Endure + Berry.
With 80 EV's placed in SpA, and a nice not hindering nature, Flygon could simply endure on the first turn, letting Salamence hit for as much as he wants, eat his berry, then proceed to OHKO with Draco Meteor (100.30% - 118.43%)
Case solved :D