Solar Plane - Possible UFO/Surveillance Drone

Saw this article on BBC website.

Solar Plane

The plane (which can be launched by hand) has a wing span of 18m and can fly at a height of 58,000ft (bit higher than concorde flies). It is silent as it uses solar energy to fly and can recharge itself. So is it possible to be mistaken for a UFO? There have been secret tests so people might not have been aware of such a plane.

There are plans to use this in space

The agency believed the vehicles could one day be used as a replacement for satellites or as unmanned drones to explore other planets such as Mars.

Are there also plans to use this as a drone for surveillance

the defence firm has continued to develop the "strato-plane" for military applications, as well as for Earth-observation and communications.

Any thoughts?

I am a newbie, so be kind and apologies if this duplicates another thread.

I've heard of this before. They've already considered these as great tools to spy on other countries. It was also a plan to use them for unmanned flights and missions to reduce loss of human casualties.