Sure, but you get a huge amount of the labor cost reduction just by going from 2 to 1 and probably have a much easier time justifying it. Labor costs are already a pretty small part of air freight costs, for instance, so proportionally, the improvement in total costs (in both absolute and relative-to-total terms) from going to 1 from 2 pilots is about the same as going to 0 from 1.
EDIT: Just to illustrate... a 777 Freighter can fly a 5000 mile route at like 500 miles per hour carrying about 100tons of freight, I think in one shift so you only need a pilot and copilot. That’s 50,000 ton-miles per hour. Air freight revenue is about $1.40 per ton-mile, so in terms of revenue, you’re talking $70,000 per hour. Pilot and co-pilot wages are much lower per flight hour than you’d imagine, around $20-50/hour, so combined, they both contribute about $70 in direct labor costs per hour, so already just on thousandth, or 0.1%, of the revenue from the freight they’re carrying. Even eliminating the pilots doesn’t reduce costs much!
Much bigger difference for smaller and slower regional air freight routes.