Genie,

It would NOT be safe in checked luggage. I believe the assumption is that the parts of the explosive would be easier to smuggle onto the flight, as the completed explosive would have a detectable chemical signature, and be caught ( with reasonable scanning) before being loaded onto the aircraft. The componants would NOT have that signature UNTIL they are mixed. It is harder to mix two liquids if one does not have access ( not impossible, just harder.) The instability would NOT be a problem if the quantity was sufficient-say half a liter or more.