The price of air ambulance services is rising.
Bills can be more than $20,000, depending on a patient's insurance coverage.
However, insurance experts say big invoices are becoming more common as costs rise and coverage shifts.
Median prices for helicopter air ambulance services doubled from around $15,000 to about $30,000 from 2010 to 2014, according to a U.S. Government Accountability Office report last year.
Air ambulances transport about 400,000 people a year in the United States, according to industry estimates.
