While serving as an exchange officer flying A-6E aircraft with the U.S. Navy at Naval Air Station Whidbey Island, Seattle, and aboard the USS Kitty Hawk, Kregel made 66 carrier landings during a cruise of the Western Pacific.

He completed one year of training and is qualified for assignment as a pilot on future Space Shuttle flight crews.

STS-70 Discovery (July 13–22, 1995) was a 9-day mission during which the crew performed a variety of experiments in addition to deploying the sixth and final NASA Tracking and Data Relay Satellite.

STS-87 Columbia (November 19 to December 5, 1997) was the fourth U.S Microgravity Payload flight and focused on experiments to study how the weightless environment of space affects various physical processes, and observations of the Sun's outer atmospheric layers.

STS-99 (February 11–22, 2000) was an 11-day mission during which the international crew aboard Endeavour worked dual shifts to support payload operations.

The Shuttle Radar Topography Mission mapped more than 47 million miles of the Earth's land surface.

This article incorporates public domain material from websites or documents of the National Aeronautics and Space Administration.