A drone operator has been threatened with a $1.9m (£1.24m) fine for allegedly flying the unmanned crafts illegally over New York and Chicago.
US authorities proposed the fine on Tuesday, saying that the firm, SkyPan International, flew 65 such flights over more than two years.
The fine would be more than 100 times larger than the previous biggest punishment.
The company said it has not had time to review the proposal in detail.
The proposed fine was so large, the Federal Aviation Administration (FAA) told the Associated Press (AP), because it had asked SkyPan to stop the flights, but the firm continued anyway.
In a statement, the FAA said that 43 of the flights were in the heavily restricted Class B New York airspace without air traffic control clearance.
The airspace is usually around airports and stretches from the ground up to a maximum of 10,000ft. It is often shaped like an inverted pyramid.
'Illegal and dangerous'
"Flying unmanned aircraft in violation of the Federal Aviation Regulations is illegal and can be dangerous," said FAA Administrator Michael Huerta. "We have the safest airspace in the world, and everyone who uses it must understand and observe our comprehensive set of rules and regulations."
It said that the firm operated the aircraft in a "careless or reckless manner so as to endanger lives or property" during the flights, which allegedly took place between 21 March 2012 and 15 December 2014. The FAA further alleged that, on all 65 flights, the aircraft lacked the proper airworthiness certification.
SkyPan is a Chicago-based firm that specialises in aerial photography. Its production co-ordinator Karl Brewick told the AP that it had not had a chance to review the fine proposal and had no immediate comment. The firm has 30 days to respond to the FAA's proposed fine.
The previous largest fine for drone operations was $18,700 (£12,200), which was proposed in September against Xizmo Media, a New York video production company, the FAA said.
On Wednesday, the day after its announcement, an FAA official was due to face questioning by a House of Representatives committee on what the agency was doing to address safety hazards created by drones flying too close to manned aircraft.
FAA officials have said they are receiving multiple reports daily of drones flying in the vicinity of airports and airplanes, Associated Press reported.