### Question
How does TRANSPORTATION OF MAIL define mainline route?


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

> a city pair in which a mainline carrier is tendered nonpriority bypass mail

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

