Flight attendants for some airlines generally receive two kinds of hourly pay.

Most of it comes during their "flight hours," which is the time between when a flight leaves the gate at its origin and arrives at the gate at its destination.

The way some airlines define flight hours means flight attendants are not always paid their full hourly rate for all of the time they spend on work-related activities.

Those tasks include checking emergency equipment, helping passengers board and exit the plane, and cleaning the plane after a flight.

Visit Business Insider's homepage for more stories.

A flight attendant's work begins well before a flight takes off, but that doesn't mean they always get paid for it.

Flight attendants for some airlines generally receive two kinds of hourly pay. Most of it comes during their "flight hours," which is the time between when a flight leaves the gate at its origin and arrives at the gate at its destination.

The contract between United Airlines and the Association of Flight Attendants-CWA, a flight-attendant union, defines flight hours as, "the time from the moment an aircraft moves from the blocks under its own power or under tow for the purpose of flight, until the time the aircraft comes to rest at an unloading point."

Read more: Flight attendants reveal 10 things they notice on a plane that you probably miss

American Airlines' contract with the Association of Professional Flight Attendants, another flight-attendant union, has a similar definition, referring to flight hours as, "that period of time beginning when an aircraft first moves from the ramp blocks at the gate for the purpose of flight and ending when the aircraft comes to a stop at the gate for the purpose of loading or unloading passengers at either intermediate stops or final destination."

Some flight attendants also receive a small per diem when they're away from their home airport for work-related reasons. At United and American, that rate is $2.20 per hour for domestic flights and a little higher for international flights.

Flight attendants aren't always paid for all of the work they do

The way some airlines define flight hours means flight attendants are not always paid their full hourly rate for all of the time they spend on work-related activities.

"There's a lot of things that we do that are kind of essential to our daily job that we just don't get paid for," said a flight attendant for PSA Airlines. (The flight attendants quoted in this story were granted anonymity due to a fear of reprisal from their employers.)

Read more: Flight attendants discuss how they're trained to handle out-of-control violent incidents aboard flights

Those tasks include checking emergency equipment, helping passengers board and exit the plane, and cleaning the plane after a flight. There's also time spent at the airport before or between flights that flight attendants don't always get paid for.

"We have a lot of airport sits where we're just sitting in the airport between flights on the concourse with everybody else, sometimes for four to five hours. You're just not getting paid," said a flight attendant for Delta Air Lines.

Some days, a flight attendant may be paid for fewer than half of the hours she works, a flight attendant for Mesa Airlines said.

"In any given day, I can work 14 hours and only be paid for six of them," she said. "That's really common."

A Delta representative said the company has four methods for calculating a flight attendant's compensation and uses whichever method produces the highest number to determine how much the flight attendant is paid for each trip. Those calculations take into account work done before or after a flight, the representative said.

"Our flight attendant compensation structure covers all elements of responsibility and work time associated with a flight — including reporting, briefing, boarding, in-flight, deplaning, and sit time, a model that is consistent with most US airlines," the Delta representative said. "At Delta, we use this structure to ensure flight attendants receive the highest pay for their trip."

First-year pay is low

Flight attendants make a little more than the average worker, according to the Bureau of Labor Statistics. As of May 2018, the last month for which data is available, the annual mean salary for flight attendants was $56,630, while the annual mean salary for all workers was $51,960.

But some flight attendants make much less than that, particularly during their first year. Two flight attendants told Business Insider they made less than $20,000 during their first year on the job.

"My first year, I wasn't making any money at all," said an American Airlines flight attendant who said she made around $30,000 during her first year. "You're so broke the first couple of years."

An American Airlines representative said the airline's flight attendants start with an hourly wage of $28.04 that reaches $64.43 after 12 years.

"We're proud to offer competitive pay and other compensation including flight benefits for all of our hard-working flight attendants," the representative said.

A Southwest Airlines representative said its flight attendants "currently earn the highest pay rates in the US airline industry."

United Airlines, Mesa Airlines, and PSA Airlines did not respond to Business Insider's requests for comment for this story.

Are you a flight attendant? Do you have opinions about how much you're paid? Contact this reporter at mmatousek@businessinsider.com.