Second, different aircrafts have different characteristics. For instance, fighters are almost always faster than bombers. Likewise stealth crafts often have lower engine power thrust due to high-sweep angles needed to deflect incoming radar waves.

3) Spot, sweep, barrage, base, and DRFM jamming have limitations based on the amount of power output provided by the craft; how many frequencies they can affect at once; and how many targets (or radar stations) can be fooled at a given time.

4) Radar absorbent material assumes a specific wave-length. Deviation from the expected frequency causes loss in radar absorption. There’s not much an advanced civilization could do about this. That is unless they can dynamically alter matter.

5) Decoys/Chaff assumes deploying some sort of metallic strip or another maneuverable flying object with the intent of deceiving radar operators. Odd as it may sound there is evidence to suggest that UFOs do deploy a form of decoy. For a good example search on Google for the 1976 Tehran UFO incident.

Heck, John even mentions in this video that JAL1628 was the first time the US govt was able to get their hands on 30 minutes of radar data and that was in 1986! At the same time to say UFOs are ubiquitously so stealthy that they can avoid all form of radar detection is a bit over the top and doesn’t have much of a scientific basing.