Part 135 & 121 definitions
 

What is the difference between a Part 135 company, and a Part 121.

I presume one is small plane charter and the other Regional above 12,500lbs or am I totally off the scale on this one?

Yes....you are.
Part 135 is non scheduled charter and air taxi operations.
Basically you call and they show up with an airplane.
Part 121 is scheduled air carrier operations.
Meaning you have to show up in time to go along on a pre scheduled flight.
Cape Air provides 121 operations in a Cessna 402.
And 135 ops can be in any size of airplane, from a 172 to a Boeing BBJ.
So size does not matter......:}

Then there is Part 91 operations, which is defined as "owner operated".
Take Coca-Cola for instance, they have a fleet of app 30 jets that operate under part 91 operations. Meaning that every employee of that company can get a ride on the airplane, also invited guests of the company.
They cannot charge their guests though because that would be providing transportation for hire.

A couple of corrections are in order here. Part 121 need not be scheduled, it can be supplemental, that is to say, not maintaining a regular schedule, but having a schedule for a particular period of time, one month, for example. However, the operator must be engaged in Common carriage, meaning anyone can buy a ticket. This is what Sun Country Airlines used to be, a Part 121 supplemental carrier.

There is a limitation as to size for Part 135 operations. The regs state that any aircraft with a payload of 6,000lb or greater and/or a seating capacity of 20 or greater must be operated on Part 125 certificate. The operators op specs will then define whether this is a charter outfit or a private situation.

Coca-Cola can charge for flights, so long as they maintain a "private carriage" status. Meaning they can transport employees of say, Dow Chemical or Mead Paper or whatnot. The FAA has held that this is permissible as long as the operator does not "hold himself out to the public" and the number of private contracts is typically not more than 3.

Part 135 may be non-scheduled or scheduled.

See 135.265.

OK I stand corrected, I gave a rough outline, didn't really want to go into all the details.:ok:

FlyBoyike:

Good explanation. I have otherwise never heard about Part 125, except from a charter jet owner in a Harrisburg (MDT) hotel about 15 years ago, who flew a presidential candidate around years ago with a BAC-111 and one or two other types. The company owner said that he had been a United pilot.