Perhaps someone will be able to answer this question.

From time to time my verizon 4G LTE air card will slow down to the point that I get multiple "Webpage unavailable" messages while attempting to surf the interweb. The net becomes all but unusable.

Almost without fail, I can then tether my Verizon cell phone to the computer and it will work at normal 3G speed. No dropped connections at all.

I do not get what causes this. Both are attempting to use the Verizon cell phone technology to make the connection. Both use the same cell tower, etc. Same cell service...etc.

What causes this?

too many fools on pandora sucking up all the bandwidth.

4g vs 3g ???

maybe the 4g signal isnt as stable as the older 3g network in the area.

The only way to tell is to test the network and see if you are having a problem and if so where it is. Good tools:

ping [ip address]

traceroute [ip address]

Also check your speed, there is a free app for iphones. And I use to use speedtest.net ... but that looks weird now.

The ping tells you speed too, use the ip address of your ISP the route to it using DNS should not change. Then a work server IP address.

There are a lot of channels or paths, you can hard code the DNS and that can help.