Find the mistake

Global business travel is a successful industry these days. Business air travelers make up a large part of ticket sales on major carriers. These frequent fliers know how to book the best fares. They can work with flight schedules. They have ways to recover from jet lag. Many of them can even work well during flights. Laptops are now the most common piece of carry-on luggage.

In this article, carriers refers to ________.



(A)
luggage handlers


(B)
people who fly frequently


(C)
people infected with disease


(D)
airline companies

I think it's D. Please confirm