### Question
How is the term existing mainline carrier defined?


### Answer
The term **existing mainline carrier** is defined in *39 U.S.C. § 5402* as the following:

> a mainline carrier (as defined in this subsection) that on January 1, 2001, was—


(A) certified under part 121

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

