6 free things you didn't know you could get on a plane

• A flight attendant reveals some surprising perks passengers can get on a flight.
• Extra snacks are free of charge and sometimes passengers can get the occasional drink on the house.
• Visit INSIDER.com for more stories.

Between the actual flight tickets, the ride to and from the airport, the extra service fees, and the pricey airport food, traveling can be pretty expensive. Luckily, there are some things you can get on the airplane for free, Melanie Glessing, a commercial flight attendant for American Airlines, told INSIDER.

Glessing said she's normally happy to give passengers whatever they ask for, but sometimes the plane doesn't have what customers want. It's important to keep in mind that some flights don't have extra things to spare and that the flight attendant doesn't have control over that. But usually, there are a few things you can ask for without having to pay any more money.

Glessing told INSIDER about six different things you can get on planes for no extra cost.

SEE ALSO: 18 things flight attendants wish you would stop doing

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Extra snacks are usually no cost.

Is that one pack of pretzels just not enough for you? Good news: You can almost always ask for more bags of snacks, free of charge, Glessing said. "Feel free to ask," she said. "Sometimes we're double-catered, depending on the flight." So, if you didn't get a chance to grab a meal (or if you didn't want to pay $16 for a sandwich), you can much on cookies, crackers, and pretzels for the duration of the flight.

Full cans of soda are usually available.

Glessing told INSIDER that if a flight has a large number of people on it, they will automatically hand out full cans of soda. But if you're on a smaller flight and would like more than one cup of pop (you're not alone), Glessing said you can ask the flight attendants.

"If someone specifically asks for the full can, we are typically happy to accommodate them," she said.

Headphones are usually readily available.

The most in-demand complimentary item you can snag on a plane? Headphones, Glessing said. "Most flights are catered with complimentary headphones," she said. "They go quick, and there usually isn't enough for each passenger." So if you forgot your headphones (again, you're not alone), you'll have to ask for a pair ASAP.