Here's the optimal route for Eye in the Sky: Eye in the Sky usually will be a 3:51 on the IGT if done well. (3:52 may be possible, but I've never seen it done)

Here's the optimal route for Airlift: Airlift usually will be a 3:54/3:55 on the IGT if done well. ^^This route MAY be fastest; it is still unsure to us but right now, the general consensus is for this route. Also, in Airlift, you can perform a glitch called "Double Grab" (shown at the very beginning of the video). I'll pin a forum post about this to discuss it more.

As far as I know, these are the fastest routes for these levels, but if something else is found to be faster, I'll update the guide.