US engineers develop spy plane that lands vertically, clings to wall

American engineers are trying to develop a spy drone that could fly silently into a city and perch on a wall for days, vertically undetected.

Stanford University is developing the technology for the "Perching Project".

A video released recently shows the team has made significant progress in getting a model plane flying at 35km/h to automatically stall near a vertical surface and hold on to the wall with its tiny spines.

Stanford professor Mark Cutkosky and student Alexis Desbiens believe the technology could lead to "a flock of small, unmanned air vehicles (that) flies quietly into a city, maneuvering among the buildings".

"They communicate as they search for places to land, not on streets or rooftops but on the sides of buildings and under the eaves, where they can cling, bat- or insect-like, in relative safety and obscurity," News.com.au quoted them, as writing.

While perched on the wall the drone could record sound and vision, and even recharge itself if needed.

A small propeller could help the plane creep along a wall until it finds an ideal spot.

After the mission is complete, the plane's hooks will disengege and it could easily fly off.