The "AIM" is a valuable resource of information for operating safely. Although not regulatory, it is a supporting document to the Federal Aviation Regulations.
Search all CODE OF FEDERAL AVIATION REGULATIONS
What is an Air Carrier? Do I apply for common carrier or non-common air carrier? Occasionally even the most experienced operator has to look at these for applicability of the FAR's.
14 CFR Part 61 - CERTIFICATION: PILOTS, FLIGHT INSTRUCTORS, AND GROUND INSTRUCTORS
Part 61 is no longer located on this site, see the eCFR website for pilot certification information.
14 CFR Part 91 - GENERAL OPERATING AND FLIGHT RULES
Part 91 sometimes addresses items that are not covered in Part 135. Examples include night currency for pilots, and take off minimums apply to operators under part 135 as well.
14 CFR Part 119 - CERTIFICATION: AIR CARRIERS AND COMMERCIAL OPERATORS
This section of the regulations addresses the management qualifications of part 135 personnel, as well as application requirements.
14 CFR Part 135 - OPERATING REQUIREMENTS: COMMUTER AND ON DEMAND OPERATIONS AND RULES GOVERNING PERSONS ON BOARD SUCH AIRCRAFT
The heart of the operational requirements for commercial operators of aircraft of 19 seats or less.