From 5W Infographics, a breakdown of how the bargain basement carriers do it:

AUTHOR
Mick Weinstein
Mick is the Head of Editorial for Covestor, a financial journalist and online content specialist. Prior to joining Covestor, Mick was for five years the Editor in Chief and VP Content at stock market analysis website Seeking Alpha, where he built the editorial function as the site attracted over 3.5 million unique monthly visitors and developed an innovative platform for intelligent stock market discussion. Mick is a graduate of the University of Michigan, Ann Arbor.
380 posts You may also like
Why investors should look at inflation-adjusted performance.
The U.S. and world economy are showing some worrying signs.
Here’s how to tweak your China strategy in a tough economic climate.
Investors may be getting way too exuberant about biotech stocks.