In Hungary a young research group (Interspect) presented a high resolution aerial remote sensing technology and the World's highest spatial resolution ortho image mosaic. It's available at www.aerialrecord.com
They made it by a Piper aeroplane (!) at 0.5 mm spatial resolution.
I've been thinking. We can do it with slow flying drones, but how can it work from an aeroplane. I heard an interview. 83 m/s ground speed requires a very fast shutter.