At any time you can alert a maximum of two rescue helicopters at once, their times of availability depend on the map and the time of day. On Lüdenscheid and Brandstedt they are available around the clock, on Linzing they are available during the following hours:
Christoph 3 - available from 5 a.m. until 10 p.m.
Christoph 10 - available from 7 a.m. until 9 p.m.
Christoph 17 - available from 5 a.m. until 9 p.m.
SAR-41 - available from 7 p.m. until 5 a.m.
The helicopters have a crew consisting of a pilot, a emergency paramedic and a emergency doctor.
There are certain medical conditions which require greater care and cannot be brought to the hospital using a regular ambulance & emergency doctor.
1. Trauma:
Gunshot wound to the upper torso 
Gunshot wound to the abdomen- Heavy bleeding
Stab wound - pneumothorax
Electrocution - Cardiac arrest
2. Internistic:
Cardiac Arrest
Circulatory arrest
3. Fire:
Burns of the 4th degree
If a ambulance cannot transport somebody due to the severity of their injuries a symbol will appear above it.
A rescue helicopter cannot land anywhere, it requires a landing spot to be designated by a police officer.
You can do this by clicking a police officer, and then clicking the appropriate button.
Now you can turn the landing zone using the scrollwheel, and finally place it using left click. Now you can select the helicopter and order it to land by rightclicking on the landing zone.
Additionally the rescue helicopter can take a patient from a ambulance. To do this, click the helicopter and then rightclick the ambulance.
Now the rescue helicopter can transport the patient to the hospital, and the police can remove the landing zone.
If no rescue helicopter is available, the ambulance chief can override the need for a transport by helicopter. The ambulance will however still be required to be escorted by a emergency doctor. You can also use the Intensive Care Unit to replace the rescue helicopter, it fulfills the same role.