Looks like I'm a bit of a 'johny come lately' and missed most of the good bits!
One problem here is that its very common for people to build their understanding of principles of flight on a foundation of dodgy Physics. Most of the issues have been thrashed out above. I know it might sound pedantic, but things like mass, inertia, momentum and kinetic energy are often not just slightly different but are truly radically different quantities.
I think momentum and kinetic energy have been well dealt with above. A brief summary:
Momentum. mv. A vector quantity. Conservative (in a given system, total momentum is always conservative, this is intimately connected to Newton 2 and 3). Pitbull top tip: Use changes of momentum to figure out how long a TIME it takes for a force to cause a change.
Kinetic Energy. 1/2mv^2. A scalar quantity. NOT conservative (total energy is conservative, any given form isn't). Pitbull top tip: Use changes in Kinetic Energy to figure out how long a DISTANCE it takes for a force to cause a change.
So we can see, they are different in pretty much every way. Don't let the fact they both have an M and a V in them fool you into assuming they are very similar - they aren't!
What about Inertia and Mass then? Not sure this has been properly dealt with. There are two aspects to mechanics, translational and rotational. Everything above (I think) was about translation, i.e. an object moving around in its frame of reference. However, there are almost identical concepts relating to the rotation of objects.
e.g. We know (Newton 1) an object will maintain a given velocity unless acted upon by an unbalanced force. The rotational equivalent is that an object will maintain a given rotational speed and orientation in space unless acted upon by an unbalanced Torque. There are equivalent concepts for momentum and angular momentum, kinetic energy and rotational energy and so on.
Inertiais a term that applies to both parts of mechanics. It is, in general, the reluctance of a body to change what its doing. The reluctance of a body to be moved is its mass. However an objects mass does not tell us much about the reluctance of a body to change its rotation. For this we need a quantity that describes not just the mass but also the distribution of the mass (remember your basic gyro theory?). This is the moment of inertia.
So, Inertia is a general term that encompasses both mass and moment of inertia.
As such, mass and inertia are not strictly identical to one another, but rather mass is a subset of inertia.
However, if you are only talking about translational mechanics then you can petty much get away with using the terms interchangeably.
Clear as mud?
pb