Air taxi vs. Charter or Part 135

"Dan" wrote in message What's the difference between "Air Taxi" and
Charter or Part 135
operations? While tracking some flights via FlightAware, I notice that
some planes fly under their tail numbers most of the time, but at times
there is a "T" prefixed to the tail number in the system. I read that
this signifies an "air taxi" operation.
How is this different from charter or 135? If they are the same, they
why are all 135 ops not prefixed with the "T" identifier?

The 'T' signifies that the flight is a commercial operator. Prior to Sept.
11, few pilots bothered to read the AIM to know this. Immediately following
Sept. 11, it was mandatory. Now it is optional, but ATC will handle the
commercial operator with confidence knowing the flight is flown by
professionals.

D.