Engines need air to function. The air are thinner at higher altitudes and engines get less air into them so there will be an optimum flight level where the engines work most effecient and enough air thickness to lift the wings and thinner air to make less wind resistance. With less cargo load an aircraft will climb faster and reach their optimum hight much quicker.
In any case, the center frequencies are much quieter now. Many folks in my companies pilot group have been commenting on it!
Fun fact, the CRJ700 and 900 have an AFM limitation that limit climbs to 1,500 fpm ([vertical] feet per minute) above 30,000'. Common to hit that wall in the 700 during the winter, but now I'm running against the limitation much more consistently. The CRJ200 has no such limitation but it would be a cold day in hell if an empty CRJ200 got anywhere close to 1,500 fpm that high.
Oh the poor CRJ200s....nothing like their younger brothers. LOL!!
Traffic is about 1/3 of normal traffic right now, so definitely much more quieter on the frequencies. The scanner folks need to remember as well that a lot of sectors are combined and are using different frequencies than you might normally expect.
I've regularly monitored 123.450 for years and seems to be about the same amount of traffic in my area of Central KY, I have noticed the huge drop in number of AC on ADSBExchange and lots of activity in mil air band.
In my area near the New Jersey coast - I have seen more CPDLC (Controller Pilot Data Link Communications) with Washington Center to domestic airline flights. Example - a JetBlue flight will come up on 127.700 (Washington Center Sea Isle Remote) and indicate to center that they are now on 127.700 after receiving a CPDLC message from center. Apparently with lower traffic levels - FAA is experimenting with using the system to communicate with less voice comms. One pilot even mentioned the same to the controller "have to use the voice comms less".
KHFF is closed UFN
KPOB/Pope has a NOTAM re everyone landing is to be screened
KVUJ which has tower manned by NCANG is shut down as well. Very little GA chatter has been heard, prob less than 50% normal and there is a flight school based there too.
Quite a bit of Mil traffic, local and transient normally around and at KVUJ and for all of March, excluding UWCULEX related traffic, i have heard one OTIS flight do some pattern work, uncontrolled airspace style, and heard the Rowan County based NCArNG H60's pass thru maybe three nights total. So that's a pretty drastic reduction as well.