The energy of the aircraft is more than enough to damage the steel, but, because the aluminum is so much softer than steel, it breaks apart first, long before it reaches the point where the steel suffers any distortion. Here are the figures:
The speed of air that will tear a plane apart at sea level densities is 500 mph.
At 500 mph air creates a force equal to 674 pounds per square foot.
If an aircraft is not carefully controlled in it's flight path, 500 mph air will rip it apart at a sea level air density of 14.7 psi.
Okay, so that's how strong or weak an aircraft is. now let's see how much force it takes to break a 14 inch box steel column.
Explosives experts will use a charge designed to move air at between 6818.2 mph and 20455 mph, which translates into forces of 125,370 pounds per square foot of pressure at the low end, to a high of 1,128,400 pounds per square foot of pressure respectively.
So we have Aircraft............ 674.23 lb/sq.ft
Steel box column:........125,370...... lb/sq.ft (low)
Steel box column: ......1,128,400.....lb/sq.ft (high)
Worse yet is the fact that the aircraft has to break several steel columns, not just one.
If the aircraft must break at any pressure above 674.23 lb/sq.ft. how
can it possibly stay intact and exert a force of over 125 thousand
pounds per square foot, to over 1 million pounds per square foot, on
the steel columns? That would be like saying that an egg could
penetrate a concrete wall if thrown hard enough. It can't. It will
crack open and spread it's force over a wide area, without ever even
coming close to generating the force needed to penetrate the concrete.
A 100 ton hollow ball of clay, moving at 500 mph, does have the energy needed to destroy a steel box column, but, because of it's softness/inability to withstand the pressure/forces needed to damage the column, it will never do any damage to the steel. Thus the plane becomes a "bug on the windshield" in effect, it splatters.