HELENA, Mont. (AP) — Blue Cross Blue Shield of Montana and Life Flight Network have reached a network agreement to provide air ambulance service in southwestern Montana, the companies said Thursday.

As part of the agreement, Life Flight Network will base one of its helicopters in Bozeman. The Oregon-based company already has a helicopter in Missoula and both a helicopter and a fixed-wing aircraft in Butte.

Blue Cross Blue Shield, which covers nearly 300,000 members in Montana, already had network contracts with hospital-based air ambulance services in Billings, Kalispell and Great Falls, as well as a cooperative in northeastern Montana.

The agreement is retroactive to April 1. It was reached after the 2017 Montana Legislature passed a bill that required health insurance and air ambulance companies to negotiate settlements of air ambulance bills, on a case-by-case basis if necessary, leaving patients responsible only for their copays and deductibles.

The legislation came out of a working group created to research the issue after Montana residents complained to state insurance regulators that they were getting hit with bills for tens of thousands of dollars for out-of-network medical flights.

"This will substantially reduce the chances that our members will have to worry about the financial burden of a large bill during a health crisis," said Monica Berner, chief medical officer for Blue Cross Blue Shield of Montana.

Insurers complained that private air ambulance companies would not negotiate in good faith or explain their rates. Air ambulance companies said insurers were making low "take-it-or-leave-it" contract offers. And patients were stuck in the middle with costly bills.

The federal Airline Deregulation Act does not allow states to regulate routes, services or prices of air carriers, and courts in several states have ruled that efforts to regulate air ambulance costs violated the act.

Earlier this month, Pacific Source Health Plans announced it had reached a network agreement with REACH Air Medical Services, which has aircraft based in Helena and Bozeman. Pacific Source previously had a network agreement with Life Flight.