The discovery could lead to planes the size of bees

Scientists say finding out how bees stay in the air - by having rigid wings up front and flexible wings at the rear - is a huge breakthrough.

The team studied insects' wings as part of a programme to develop aircraft smaller than the human hand with cameras and sensors built in.

The discovery could lead to tiny planes being built for use in spying and fire and rescue operations.

"This is a very important step forward in understanding how we can create tiny aircraft that could be so useful for us," said Professor Ismet Gursul, in the University of Bath's Department of Mechanical Engineering, who heads the team at Bath.

Spy planes

"Large aircraft like the ones we fly in don't have to produce vortices for propulsion, so they can have fixed wings and engines, but we have found that smaller ones will have to take a leaf out of nature's book if they are to work efficiently.

"Our work will make the goal of tiny aircraft, perhaps eventually the size of bees, a step closer."

Professor Gursul, who is giving a public lecture on his work on vortex flows at the University on Wednesday, said small aircraft a few centimetres in size had already been built in the US and flown, but these could only stay airborne for a few minutes.

His team's work will allow them to stay in flight for longer, but more work is needed to find ways to power the craft more efficiently.

If this is a success then the micro air vehicles could also be used as spy planes, sending back clear, detailed video footage of battlegrounds, allowing commanders to use their troops more effectively and avoiding the need for human scouts to risk their lives.