It's basically luck where shrapnel from any missile hits a plane.
If it's the wing or fuselage, the damage to the airframe could lead to the aircraft breaking up from aerodynamic forces.
Of course, a plane could get lucky.
https://en.wikipedia.org/wiki/2003_Baghdad_DHL_attempted_shootdown_incidentIn this case, DHL's A300 got lucky, the shrapnel only damaged the hydraulic systems on board. The flight control surfaces remained in a neutral position as a result of Airbus' design, and the pilots were able to fly the aircraft and land using differential thrust only. While the skill of the pilots was a major factor, the fact that the A300 managed to keep flying level and stable saved the aircraft and crew. Had the shrapnel struck a different part of the plane, however, it would have been a very different story.
I'm not going to attack the 737 NG design here... because it's basically luck where the aircraft gets hit by shrapnel. That, and civilian airliners aren't typically designed to withstand being shot at. The likes of the C-130, C-17 and A400M would have their designs consider the likelihood of being shot at... but those are military transport aircraft, not civilian airliners.
