It depends on who is doing Smart car crash test for the results to vary. There was a report from PCMAG.com in April 2009 stating that the Smartfortwo car went airborne and turned 450 degrees. This is the result of a head on crash with a Class C Mercedes at 40 MPH. Since the car only weighs in at 1500 lbs, going airborne is because it is so light weight. This article made it sound like a bad thing. Consider the alternative, staying on the road and being crushed. An impact that causes the car to lose its footing so to speak would be preferred. Less damage, but what a wild ride to take would be one for the storybooks.
The Insurance Institute is the standard by which all cars sold in America are tested. Even with most Americans seeing this small car as dangerous compared to all the rest, it still got the highest ratings possible by the institute of good. This was for both the front and side impact.
It is true that the bigger the car and heavier the car, the safer it is for you inside. But this is what has made it so dangerous for people that want to get good gas mileage. Most American think big when it comes to owning a vehicle. Detroit has kept building bigger and bigger cars. When the cars were downsized most Americans started to buy trucks and SUV's.
Europe has already downsized to small and compact cars like most of the rest of the world. If Americans ever want to stop depending on foreign oil, they will learn not to drive a tank around. With more small cars on the road, the smart car crash test will be a more common result when one is in an accident instead of one going airborne when it is hit by a tank.