TOP-secret pictures have captured Amazon's covert aerial delivery drone tests.
Engineers donning orange hi-vis jackets were snapped testing the drones at a base in Cambridgeshire.
The photographs taken by the Mirror, captured its test programme that has been kept a secret since 2016.
The engineers were reportedly assessing safety concerns and trying to improve the drones battery life, the newspaper reported.
An expert said: "If you have to recharge them every other hour, then you need so many drones and you have to orchestrate that.”
The Civil Aviation Authority said Amazon has not yet applied for the drone technology to be approved.
Boss Jeff Bezos previously announced his plans to use drones to deliver packages in 30 minutes.
In 2013, he predicted drone deliveries as he said: I know this looks like science fiction, it's not. Could it be four, five years? I think so."
Drones have come under scrutiny following the travel chaos sparked at Heathrow last week and at Gatwick last month.
On Wednesday passengers reported seeing a police helicopter overhead while another told The Sun Online they were on the tarmac when the airport suspended all operations.
A video supposedly showing the drone over the area was obtained by The Sun Online.
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