Or just simply:
Step 1: type /world (1-99 [whatever, if you're alone there] (like /world 74)
Step 2: type /taxi 0 to get in the ship
Step 3: Walk/Drive closer to the 4-dragons casino, but don't go that far
Step 4: During the road You'll see a huge pillar
Step 5: use /world gravity -0.15 to get up
Step 6: When ur up do /taxi and then do /world gravity 0.001
Note: If you get stuck under the floor, you can try jumping, or just do /dive after ur in that part. (It'll get throught the floor eventually)
Now you're up.. Much faster than waiting for a helicopter or a plane to spawn/distances between Airport and the Strip