Saw this story on the BBC news tonight about the new NASA telescope (Sofia) ready to launch in a 747. It's so sad that the best news on American science tends to come from the BBC. Anyway, this looks really cool - huge jet jammed full of scientific equipment flying around every other night with its cargo door open and a big telescope taking pictures above the clouds. I imagine the biggest challenge was compensating for the vibration of the plane.
http://news.bbc.co.uk/2/hi/science/nature/8638566.stm