The US government agreed to a police request to restrict airspace surrounding Ferguson, Missouri, for 12 days in August for safety, but audio recordings show local authorities privately acknowledged the purpose was to keep news helicopters away during street protests.
Such images would have offered a clear view of one of the most serious recent episodes of civil violence in the country.
On August 12, the morning after the Federal Aviation Administration imposed the first flight restriction, FAA air traffic managers struggled to redefine the flight ban to let commercial flights operate at nearby Lambert-St Louis International Airport and police helicopters fly through the area - but ban others.
"They finally admitted it really was to keep the media out," said one FAA manager about the St Louis County Police in a series of recorded telephone conversations obtained by the Associated Press.
"But they were a little concerned of, obviously, anything else that could be going on."
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At another point, a manager at the FAA's Kansas City centre said police "did not care if you ran commercial traffic through this TFR (temporary flight restriction) all day long. They didn't want media in there."
FAA procedures for defining a no-fly area did not have an option that would accommodate that.
"There is really ... no option for a TFR that says, you know, 'OK, everybody but the media is OK,"' he said.
The managers then worked out wording they felt would keep news helicopters out of the controlled zone but not impede other air traffic.
The conversations contradict claims by the St Louis County Police Department, which responded to demonstrations following the shooting death of 18-year-old Michael Brown, that the restriction was solely for safety.
Police said at the time, and as recently as late on Friday, that they requested the flight restriction in response to shots fired at a police helicopter.
But police officials confirmed there was no damage to their helicopter and were unable to provide an incident report on the shooting.
The Associated Press obtained the recordings under the US Freedom of Information Act.
It said they raise serious questions about whether police were trying to suppress aerial images of the demonstrations and the police response by violating the constitutional rights of journalists with tacit assistance by federal officials.
The flight restrictions, which applied to more than 95 square kilometres of airspace surrounding Ferguson, remained in place until August 22, FAA records show.
