United Airlines trained their flight attendants to use CRM in conjunction with the pilots to provide another layer of enhanced communication and teamwork. Studies have shown the use of CRM by both work groups reduces communication barriers and problems can be solved more efficiently, leading to increased safety.[8] CRM training concepts have been modified for use in a wide range of activities including air traffic control, ship handling, firefighting, and medical operating room, in which people must make dangerous, time-critical decisions.[9]