If you die before defeating Ripburger, load last save to try again. If it's past beyond this point, you'll have to start all over again. The end sequence is limited, so don't waste your time.
For the front of the truck, use your hand to open the engine grate. This will be your opportunity to pop the Rabbit Ragu achievement/trophy where you must put a rabbit into the engine fan. You then have to use your hand on the panel between the engine and the windshield. Ripburger will try to close it with the cane, so grab it immediately, and then use it on the engine. The engine will stall and Ben will go through the engine compartment. Once he emerges in back, use the tire iron on the upper right hose. It may be tough to see, but there's a nut (about two sections) from where the hose is connected. Once you use the tire iron from here, another cutscene starts. Achievement/trophy for "Now Boarding" pops once you're inside the plane.
Once so, use your hand on the ladder once to have Ben walk in front of the truck, which in turn, he'll get shot at. Do this again, to finally climb up into the cockpit. Click on the mid panel. Select Take off, Post take off, Gear,
and Raise gear.
After a short cutscene, you'll regain control of Ben on the truck.
ANOTHER OPPORTUNITY NOTICE: For the "Looming Seagull" achievement/trophy, go into the truck, click the button under the middle display and press: Main Menu, Defense systems, Machine guns,
Again, you must go into the truck cab, click on the button under the mid display, and this time, enter the following: Main menu, Defense systems, Machine guns, Control,
and system off
to pop the achievement/trophy.