Delta Air Lines is testing out a system to allow customers to use SkyMiles to pay for fees for services like wi-fi, pets on board, unaccompanied minors and change fees.

"We're piloting this year using miles for fees," said Delta president Glen Hauenstein during the company's investor day Thursday. He said the company wants travelers to be able to pay with their miles "to allow this to be a living currency."

In dollars, fees for unaccompanied minors are $150 each way. Carrying on a pet cost $125 each way on domestic flights, while traveling with pets as checked baggage costs $200 on domestic flights.

In-flight wi-fi rates vary, but Delta charges $16 for a day pass for wi-fi on domestic flights.

The airline charges change fees of $200 for domestic flights, and up to $500 to change international flights.

Delta gave few details about the pilot test using miles, but Hauenstein said: "People who fly us all year round on business and then they take their family to Hawaii and they want to stay an extra day and we charge them those $150 change fees -- We want them to be able to pay with their miles."