.45 Mach is actually 345.271 miles per hour which is a really fast drone that takes off from aircraft carriers

The Pegasus drone is one of the few unmanned aircrafts that is designed for aircraft carriers. The drone is huge and is designed to cruise at 0.45 Mach and can attain speeds of over 180 mph. An important feature of the Pegasus is that it can easily take off from the ground and land all by itself, in addition to refueling over the ocean. It can also be fitted with smart bombs and other weaponry that can self-deploy using the onboard computer systems.

X-47B PEGASU

By the way I have also seen videos of this thing being refueled in the air as well. So, it can stay up as long as it is being refueled periodically I guess.

by the way Self-deploy of weapons means no humans need to be involved to launch weapons once it has been given permission to act on it's own.