The revenue earned by airlines through extras such as baggage fees and add-on seat charges continues to grow by the billions.

Dino Flammia, Townsquare Media NJ

According to an analysis by IdeaWorks, which looked at the financial filings of airlines worldwide, ancillary revenue topped $38 billion in 2014, up from $31.5 billion a year prior.

The per-passenger ancillary revenue hit $17.49, which is 8.5 percent more than the 2013 result, the analysis said.

While travelers at Newark Liberty International Airport insist the fees have gotten "ridiculous" over the years, they admit they're still putting out the money. And if the people keep paying, why should the airlines stop?

"I have one extra baggage and I had to pay $120 for it," said Jorbe Koroma, waiting for her flight to London. "And because the baggage is overweight as well, there's an additional charge of $50."

Koroma also paid the fee for an upgraded seat, offering her extra leg room and lounge access.

Detroit resident Ashna Merchant, resting during her five-hour layover in Newark, said she remembers the days of at least one free bag on domestic flights, and those days no longer exist.

"We had to pay like $125 for one bag just for clothes for a week," she said.

It is possible to get creative in order to avoid certain fees, but one must have the patience and the courage.

"You try to pack your carry-on and pretend you don't have it," said Neri Gudaitis of Connecticut.

Cited as the biggest earner of these add-on fees, a spokesman for United Airlines noted the latest research also includes revenue the airline earns from its credit card partners.

"Of course, these revenues, while counted in the research, have no connection to what travelers pay when they travel," the emailed statement said.

The airline said revenues, whether from passenger travel or ancillary earnings, have funded 200 new aircraft over the last five years, high-speed in-flight Wi-Fi and extensive terminal modernization in at least six airports, among other things.