Step 1: The Titan usually spawns when you're half way to getting to level 34, if it doesn't, then get someone who has the ability to spawn it, or buy it Online for $2,000,000.
Step 2: Go to the rear left of the door and punch it, it should come down.
Step 3: Get in the plane, drive forward slowly until it comes down. When it comes down...well it's up to you now since the door is down.
Step 4: Please don't put cars in it, put bikes and motorcycles in it since they slide back slowly. And it's easier to control them.