Can astronavigation be used during flight? In an aircraft, can you look at the sky to get your bearing and position like sailors do?
You sure can! It's not really done all too much any more in the days of GPS but it was done quite a bit in the early days of aviation. Historically, this was done by the "flight navigator" a position that no longer really exists. Some aircraft even had mounted sextants.  



(source)

Here is a video of it being done in practice (fanta optional)

This was even automated on the SR-71's Inertial Astro-Navigation system which used the stars to align itself.