On the evening of March 20, Baltimore police officers trying to find a missing 9-year-old girl called for backup, and one of the department's four $1.2 million American Eurocopter EC-120 helicopters swooped over Cherry Hill.

An officer in the copter couldn't find the child, but using the onboard bull horn, he shouted for her to call 911 or her parents.

The girl heard the plea, and 15 minutes later she walked into her house and into the arms of her worried mother.

It was one of thousands of searches performed each year by Foxtrot, the collective name for the city police aviation unit's helicopters. They were purchased in 2001 to replace the two-seat Schweitzers that had been grounded in 1998 when one crashed into the roundhouse of the B&O; Railroad Museum, killing the pilot.

But now, the helicopter unit is threatened by budget cuts, targeted in a preliminary proposal by City Hall that also could slice hundreds of officers from the force.

Helicopters don't come cheap, though it's a small part of the Police Department's $315 million budget projected for the next fiscal year. It cost $2 million a year to keep the helicopters aloft and another $2.1 million a year for the 27 pilots and officers who ride in the passenger seats and maneuver the cameras and watch the city.

Some residents have called the helicopters nothing more than expensive toys that annoy homeowners with bright lights and noise, and they wouldn't be sorry to see them gone from the skies.

One reader pleaded on The Baltimore Sun's Crime Beat blog for detailed stats. Another took one of the few numbers initially offered up by the department - that Foxtrot had assisted officers in 4,300 arrests since 2001 - and wrote that it "works out to $8,372.00 per 'assist.' Yes, you can put a price on human life, that's too much money for too little return."

One of the most common queries police reporters get from readers: I saw the helicopter flying over my house. Can you tell me why? Residents assume the worst has happened if the cops called in a chopper, even if the pilot is shining his light to help an officer on a routine traffic stop at night.

The Police Department's chief spokesman has called the potential loss of the choppers "devastating." But quantifying what pilots and observers do as they patrol the city from above, sometimes 17 hours a day, has never been easy.

Newly obtained2009statistics provide guidance and might help soften critics who feel money for the helicopters could be better spent on more police in patrol cars.

Foxtrot flew 3,847 hours, responded to 7,522 calls for service and assisted in 402 arrests. Crews handled 94,643 incidents, counting everything from photos taken during surveillance flights to flying over the harbor and port as part of Homeland Security duties. The helicopters helped clear almost as many drug corners (9,411) as they did fly over dump sites (9,607) to determine whether people were improperly disposing of trash.

The police observers riding in the copters used their cameras 2,889 times, the LoJack car theft system 122 times, the public address system 1,186 times and turned on their sirens 2,200 times. They used their infrared night vision 4,999 times and made 28,576 Homeland Security checks on watersheds, commercial and industrial targets and the harbor and port.

Critics of the mayor's budget process have called the threatened cuts nothing more than scare tactics to win support for more fees and taxes, and argue that officials have no intention of cutting police and the helicopters when the city is celebrating decades-level lows in homicides. Police Commissioner Frederick H. Bealefeld III has warned that the cuts could set the city back years in terms of combating crime.

In a campaign to save the copters, police officials have begun collecting reports on Foxtrot's activities, and they told me about a small sampling of recent activity culled, I'm told, from documents compiled for the police communications division.

•On March 24, police investigating a gun discharge and a carjacking in Baltimore County had the helicopter follow a black Acura with a missing front bumper until it stopped and officers could arrest two men without getting into a high-speed chase.

•On March 26, the officer riding in Foxtrot located a car on Pulaski Highway whose occupants were suspected of buying drugs. The pilot followed the white Infinity until officers stopped it at Orleans and St. Paul streets and arrested the driver. Police seized an assault rifle, $14,000 and an ounce of suspected cocaine.

•On April 5, Foxtrot flew over a house on Whitney Avenue in Northwest Baltimore to help officers investigate a burglary. Using the spotlight, an officer in the copter spotted a suspect inside carrying a suitcase. The officer watched as the man tried to climb out several windows before being arrested.

Police departments in Anne Arundel, Baltimore, Howard and Prince George's counties also have aviation units, as do Maryland State Police.

In 2009, Baltimore County flew its three Eurocopter helicopters a total 1,856 hours and assisted in 338 arrests, 1,632 searches and 10 pursuits. The helicopters helped to find 14 missing people. Their budget is $1.8 million in operational costs.

According to the U.S. Department of Justice's Bureau of Justice Statistics, three of every four police departments in the country with more than 1,000 officers had an aviation unit in 2007. They employed more than 3,400 people, using 900 aircraft, and logged more than 363,000 flight hours.

Comparisons were hard to make, and the study does not provide costs for each department. But it appears Baltimore police fly their helicopters more often than most medium-size to large departments.

The Los Angeles Police Department, for example, has 18 helicopters and one airplane and flew 17,048 hours in 2007. The New York Police Department has seven helicopters and flew 4,449 hours in 2007.

Philadelphia police flew their two helicopters 1,200 hours in 2007. The Metropolitan Police Department in Washington flew its two helicopters 891 hours that same year.

But since that analysis was done, other police departments have shut down their aviation units to save money. The Colorado Springs Police Department shut down its helicopter unit, reassigning three full-time pilots and putting two vintage helicopters up for sale. Departments in Tulsa, Okla., and Oakland and San Bernardino, Calif. also eliminated their units, according to The New York Times.

But Baltimore could be the first major urban force to ground its air support.

And that has city officials scrambling to prove that the copters are more than toys bought with federal funds that also have helped supply police departments across the country with armored vehicles and paramilitary SWAT teams after the attacks of Sept. 11, 2001.

The Department of Justice study notes that most of the nation's police helicopters are equipped with spotlights and infrared thermal imaging devices, both of which allow officers to see at night.

Taking pictures, surveillance, helping on routine patrols and pursuits were the most common activities listed in departments across the country as well as in Baltimore.