Primary health insurance providers usually only pay to transport a patient to the closest hospital or medical facility. If you are over seas and need to get home, most likely your normal insurance provider won’t cover it.
There are insurances that are specific to air ambulance coverage. Here are links to a few of them:
Air Ambulance Card -Prepaid medical transportation
Isis – Insurance company offering air ambulance program
Medex – Insurance company with air ambulance coverage
MASA – Mexico Insurance Professionals