The Air Support Unit (ASU) was a Central Operations branch of London's Metropolitan Police Service. The main responsibility of the unit was to provide aerial reconnaissance and other air support operations. Helicopters are particularly useful in aiding searches for missing persons, car pursuits, suspect capture and large public order operations such as football matches. The ASU also supported other emergency services, including the London Fire Brigade, London Ambulance Service and Marine Coastguard. On 31 March 2015, the National Police Air Service took over providing air support to the Metropolitan Police Service (along with all other police forces in England and Wales). This resulted in the closure of the Metropolitan Police Air Support Unit.