Company officials plan to contact hospitals and emergency medical services agencies to make sure transportation is available to patients.
Air Angels CEO Jim Adams says in the statement the decision is based on "recent and ongoing events" without being more specific about those events.
There are some options left for patients who need emergency transportation in Illinois.
Superior Air Ambulance lifted off from the base at the DuPage airport on Thursday night. The company is the most recent chopper ambulance service in the Chicago area and they figure to be a little busier with Air Angels no longer flying.
"I don't see any risk to the public safety," said Jay Washburn, vice president, Superior Air Ambulance. "I'll still be able deliver the high quality care."
The Air Angels equipment is already under wraps at the airstrip in Bolingbrook where they are based. The company ceased operations immediately on Thursday issuing a statement saying, "recent and ongoing events lead us to believe that our venture is Illinois is no longer viable. A great deal of effort and exploration and research has gone into making the difficult decision to close Air Angels."
Last August, the crash of an Air Angels helicopter in Aurora killed all four people aboard including the 14 month old patient Kirsten Blockinger. Her parents have filed suit against Air Angels alleging unsafe practices and they testified before the NTSB earlier this month.
"I do believe her accident was preventable and it's unacceptable," said Brooke Blockinger, Kirsten's mother, on February 3.
The crash and others prompted the NTSB to review safety procedures for medical helicopters which have been involved in 85 crashes in the last six years. That has prompted increased safety measures for Superior and other companies.
And for pilots and paramedics who routinely deal with life or death situations for patients they say the more focus on safety the better.
The Associated Press contributed to this report.