I researched an article back in 2002 so I know this is further advanced now-
"Today most of the major and even not so major, aerospace companies are in development of UAVs with many contracts up for grabs. There exist today tiny insect-sized recon devices that can fly into a building via silent, sub-miniature electric motors and gather images with TV cameras the size of a fly's eye. One is even powered by a "device that converts chemical energy into reciprocating motion through a direct non-combustion chemical reaction." It uses one propellant, has no flame or visible exhaust and can operate without oxygen. This is not sci-fi, it's happening now. MAVs (Micro Aerial Vehicles) of larger size abound in number with weight measured in grams and size in the less than 6-inch range."
As for sinister big spy planes I found this theory presented a few years ago too-
"It's been pieced together that the Aurora is carried aloft by a C-5 (good idea- less visual exposure) to 35,000 feet where its huge clam-shell doors open and the ship is extended via a hoist arm as it powers up. Wing tips unfold and lock as the plane is dropped to then fly under its own power. It climbs to well over 100,000 feet by using a turbo-ramjet engine ingesting exotic methane or hydrogen fuel as it travels at 3,800 MPH to survey its designated target. Once the mission is complete the Son of Blackbird would meet up with another or the same C-5 where the boom would extend, capture would occur, the wing tips folded, and it would be swallowed up inside the massive mother ship."