Bad Piggies Flight in the Night Bonus Level 4-I (4-1) can be 3-starred in two steps. King Pig makes the contraption far too heavy to beat the clock, but in general, this is a very straightforward level. With King Pig, freckled pig, and egg on board, slowly make your way downhill using the bellow to safely reach the end. To beat the clock, leave King Pig behind and make the contraption smaller.
If you have a different strategy for completing this level feel free to leave a comment below.