Long waiting times and increasing costs of helicopters have led to police investing in drones instead, a watchdog has found.
Around two-thirds of forces in England and Wales own or have access to unmanned aircraft and only six are not considering using them, according to a report.
The amount spent on the technology varies hugely between forces, with Surrey Police and Sussex Police jointly spending £300,000 on five drones while Durham Constabulary bought one for £1,450.
A report by Her Majesty's Inspectorate of Constabulary and Fire and Rescue Services into the National Police Air Service (NPAS) has raised concerns about the piecemeal approach to unmanned aircraft in different forces.
Guidance for police on how and when to use drones and other air services was "patchy at best" and has led to "confusion among frontline officers" about their use, it added.
"While most forces have purchased drones, none has rigorously evaluated their use and, as a result, the police service has not developed a common view on their relative merit as a form of police air support," the report said.
It found that:
:: A total of 28 forces in England and Wales have purchased or have access to least one drone.
:: Most have purchased two or three and the Metropolitan Police has 12.
:: Another nine forces are considering purchasing or arranging for access to the technology.
:: Only six forces have not formally considered drone use.
:: The cost of individual drones bought by forces ranged from £1,450 to £60,000.
The report has called for an evaluation of the cost-effectiveness and potential uses of drones, which are not currently operated by NPAS.
Mark Burns-Williamson, chairman of NPAS and West Yorkshire Police and Crime Commissioner, said: "It is widely acknowledged that NPAS has achieved a lot but that there is a need to consider the next stage of development for the service including a clear user requirement for police aviation and how drones can impact on the wider service.
"We had previously submitted a bid for transformation funding on the use of drones which was unsuccessful but this work clearly needs to now be addressed by the National Police Chiefs Council (NPCC) and NPAS."