### Question
How does the law define part 121?


### Answer
Under *39 U.S.C. § 5402*, **part 121** is defined as:

> part 121 of title 14, Code of Federal Regulations

#### Citation:
  - *39 U.S.C. § 5402*
  - Heading: **PART V-TRANSPORTATION OF MAIL > CHAPTER 54-TRANSPORTATION OF MAIL BY AIR**

