With all due respect, I'm not sure you are giving proper consideration to the power of good recon.
Notwithstanding the Thracian's poor flying skills, the Cub is a fairly easy aircraft for beginners to pilot. That said, a few quick sorties on the morning of the engagement might have revealed Mummius' flanking movement and changed the course of the battle.
Even if the Thracians were routed and driven southward, Crassus' delay in pursuit would have given Spartacus ample time to ferry his troops, one by one on the plane, to Sicily where they could have regrouped and carried on their raids from the safety of the island.
In short, the war would have certainly lasted many more months.
No fuel, no flight.