What is the difference between being instructed to land “as soon as possible” or “at nearest suitable airport”?

On commercial airliners, the FCOM (Flight Crew Operating Manual) sometimes gives instructions to the pilots to land sooner than planned, following various in-flight failures or emergencies. For instance, for serious emergencies (e.g. in-flight fire), the pilots would be instructed to LAND ASAP (as soon as possible), as there is a real danger to the aircraft and its occupants if they stay in the air any longer.

For less severe situations, the pilots would be instructed to LAND ANSA (at nearest suitable airport), which gives them more leeway in deciding where to land.

My question is: other than the fact that LAND ASAP is obviously more urgent than LAND ANSA, could anyone go into more details as to how a pilot would interpret these instructions, and how they differ? (for instance, does LAND ASAP mean "land on the nearest reasonably smooth surface", or is it less extreme than that? Are there guidelines on approximately how long you should keep flying after receiving a LAND ANSA instruction?)

• In the planes I fly, ASAP means pick the open field in your vicinity which is least likely to kill you and land there. Don't know this applies to airliners though. :) – falstro Jun 19 '14 at 8:28