NEW: DHS Secretary Markwayne Mullin says he owes the U.S. Coast Guard pilots a huge thank you after his plane was forced to make an emergency landing. The unexpected stop was due to an engine failure while flying from Georgia to Washington, D.C. "The U.S. Coast Guard pilots made the single-engine landing feel routine. No panic, just straight professionalism." The aircraft is one of several Coast Guard planes DHS flagged last year over concerns about the fleet's age.