A mystery plane has been carrying out surveillance work over the skies of Bletchley and southern Milton Keynes over the last week.
But boffins from the Open University who commissioned the project say not to worry, as it is actually part of a scheme to monitor how energy- efficient local homes are.
One reader, who asked not tbe named, said: “On Sunday evening we went for a stroll.
“Above us a small propeller aircraft kept flying low, backwards and forwards, over Old Farm, Browns Wood and Wavendon Gate. It went on for an hour and a half.
“We asked the police who made some enquiries. They told us that it was an ‘organised survey’ but they couldn’t tell us who was doing it, what for or why.”
The work was commissioned by Gerd Koprutm, professor of computing at the OU, for the MK:Smart project being run in collaboration with Milton Keynes Council.
This includes work developing a tool to assess the green energy potential of homes and commercial properties.
The plane is believed to have flown 3,843ft (three-quarters of a mile) above the ground, travelling at an average of 143mph.
An OU spokesman said: “Part of this project is to test if it’s feasible to use aerial imaging to determine building energy efficiency parameters.
“There are flights over MK at night to collect thermal data, these are thermal images resolution 50cm, not photographs.”