Originally Posted by
Jughead
I'm pretty sure the 88 and the 90 will capture the altitude in VNav even if the ALT is not armed. I don't attempt to do this on a regular basis, nor would I recommend it to my buddies.
I don't think
either will capture altitude in VS or IAS mode if the ALT isn't armed, but I haven't played around on the 90 enough to act like I'm an expert.
I
do watch the FMA like an expert when approaching an altitude, no matter what I'm flying.

It will capture whatever altitude is in the Cruise page, but only in VNAV, if you have it in FTB mode, see:
Here it has four options left, which is better than being out of options. It sucks to be out of options in an MD88.