Kathleen (Kay) Hilbrandt started taking flying lessons in 1942, and in 1943 was accepted into the Womens Airforce Service Pilot (WASP) program. She attend Army Air Corps flight training (the same course as male pilots) in 1944, flying PT-17s, BT-13s and AT-6s. Then she served as a safety pilot in Eagle Pass, Texas, for aviation cadets performing instrument flights "under the hood".

After the war, when the WASP was disbanded, she joined the Ninety Nines and returned to New Jersey to work for Bendix Aviation Corporation. Following that, she was a flight instructor, training veterans who were using their GI Bill to obtain flight training.

In 1960 she flew in the All Women Transcontinental Air Race ("Powder Puff Derby") in a Cessna 172.

In 2010 the WASP were awarred the Congressional gold Medal for their service during WWII.

In 2013 Kay received the Wright Brothers Master Pilot Award. She continues to fly for pleasure.