[MediaMole]

They are apparently used to destroy drug crops in foreign countries. One could logically assume the plane was being flown back to the US in case it was needed to destroy poppy crops in afghanistan.

An alternate hypothesis: it was being flown back to the US to avoid any possible terrorist use.

[TrappedInLiberalHell]

This sounds like the kind of thing that probably happens much more often than we realize, but is more noteworthy now because of recent events. All the same, it would behoove us to find that plane ASAP. Not just because of the risk of bioterrorism, but to save the pilot's life, if at all possible. I haven't seen anything on the news sites yet, other than Drudge. This must be unverified as yet. I hope it's a rumor, or that the plane has been found.

[piasa]

Could be.

[mcollins]

"They are apparently used to destroy drug crops in foreign countries."

Bingo.