In theory, yes, but in reality that's less and less likely to be doable and is largely only kept around because it is a law mandated by Congress.

The amount of time spent training a pilot just to fly a modern jet fighter, much less train them in the tactics and qualifications needed to fly such jets in combat (and to operate the incredibly advanced avionics today), is far beyond the old WW2 model of training and building/restoring fighters as the war progresses - especially since older planes have far fewer systems than today.

Take for instance, to be a Navy F/A-18 Super Hornet pilot today:

• 6 weeks of Aviation Preflight Indoctrination (basic aviation knowledge, basic survival skills, altitude chamber, water survival, etc.)
• 6 months at Primary Flight Training in the T-6B Texan II (basic flying skills, aerobatics, formation flying introduction, and instruments)
• 9-15 months at Intermediate Jet/Advanced Strike in the T-45 Goshawk (learning to fly the carrier landing pattern, 2-plane and 4-plane formation, instrument rating, bombing pattern, low level flying, basic dogfighting, and finally culminating in your carrier qualifications)
• 9-12+ months at the Fleet Replacement Squadron learning how to fly the F/A-18 Super Hornet, systems operations (especially the radar and various weapons systems), getting carrier qualified in the Super Hornet, etc.

All that? Congratulations, you can now fly as a combat wingman in the fleet to someone senior to you. Now start working on getting qualified to be a two-plane lead and then work your way up to be a four-plane combat lead.

As you can imagine, 4-5 years have passed by this point - most modern wars that have attrition rates that would necessitate active replacements will have ended by then.