Related Clues:

• Aircraft tracker
• Sub sighter
• Tracking method
• Speed detector
• Motion picker-upper
• Sunken ship finder
• Warning system
• It can pick up a plane
• Under the __
• Control tower tracking device
• School locator?
• It might set off a light
• O'Reilly of 'M*A*S*H'
• Underwater wave generator
• Sub's ears