All totaled, our first quarter adjusted operating income increased 56% year-over-year primarily due to international priority volume growth of 31%, a surge in demand for U.S. residential delivery, yield improvement at FedEx Ground and FedEx Freight, a $130 million benefit from an additional operating day, a $65 million benefit from a reduction in aviation excise taxes provided by the Cares Act and a better alignment of our expenses, especially at FedEx Freight.
Refer to the input text as context and select the correct relationship between 'FedEx Ground' and 'FedEx' from the available options.
Options: founded by, currency, owned by, parent organization