JMSDF's Commissioning of SS-504 Zuiryu

[SvenSvensonov]

Seems understandable that it's a natural technological evolution. I guess in the near future differences would less and less, so one would have to come up with innovative ways to detect submarines.

Fow ASW aircraft like P3 and P8, what is the maximum altitude/speed they can fly at and still have a reasonable chance of detecting a submarine, say that has gone 200 meters deep?

For the P-3, P-8 or any other ASW aircraft, they can remain at cruise altitude and cruise speed and still detect a sub 200 meters or deeper thanks to the aircraft itself not being the one to detect and track the aircraft. Yes the MAD on a P-3, or hydrocarbon sensors on a US P-8 will be used for tracking and detection, but only after sonobouys have indicated that a sub is in the vicinity. Typically ASW aircraft are only searching for a sub if one is suspected of being present. How that suspicion comes is up to each nations individual operating capabilities such as regional suspicions, over zealous and vocal media (as seen with China's type 039a in Sri Lanka), underwater sensors, satellite tracking, some other platform will notice an anomaly, leading the ASW aircraft to the area. Sonobouys will confirm the suspicions and once the suspicions are confirms, at cruising speed and altitude, an ASW aircraft can begin a trace and track. And yes the sensors on a US P-8 are sensitive enough to track a submerged sub while flying at cruising speed and altitude.