Police helicopters and aircraft offer incredible advantages to officers on the ground. They are especially helpful at tracking vehicle pursuits, even taking over as the "lead" in the pursuit to prevent ground units from taking unnecessary risks. At night, the air units need technology to track the suspect vehicle.
While spotlights are the most common means of tracking at night, they offer the distinct disadvantage of informing everyone nearby, including the suspect, exactly where the airborne officers are looking. By mounting a thermal imager on an aircraft, officers can gain a discreet, yet effective, monitoring system that allows them to track suspects without their knowledge. This makes the pursuit safer for officers, the public, and even the suspects.
Once the bad guys hear the whup-whup-whup overhead, they'll be surrounded by ground officers and know that things are about to go south--the way it should be.