A detector plane is an aircraft equipped with specialized equipment to detect objects or signals. It is typically used for military purposes, such as locating submarines or detecting enemy aircraft. The four crossword solutions for the term 'detector plane' are SONAR (5 letters), METAL (5 letters), RADAR (5 letters), and NOSE (4 letters). Sonar stands for Sound Navigation and Ranging and is a system that uses sound waves to detect objects underwater. METAL is a material that can be detected by RADAR, which stands for Radio Detection and Ranging and is a system that uses radio waves to detect objects in the air or on the ground. Finally, the NOSE of the plane is often equipped with sensors to detect objects in the air.