John Nance on Concorde Crash

July 25 -- An Air France Concorde jet crashed near Paris today shortly after taking off from Charles de Gaulle airport. According to the French Interior Ministry, all 109 people on board were killed. The plane hit a hotel and restaurant before crashing into the ground.

The plane’s engine was on fire, said one eyewitness, and a huge cloud of black smoke was visible in the air. What could have happened to cause such a fire? Could it be related to the cracks that were recently discovered in the wings of several Concordes?

ABCNEWS’ aviation analyst, John Nance, joined us for an online chat about the crash. A transcript of the chat appears below.

Moderator at 2:55pm ET

Welcome, John Nance. John, do we have any news yet as to what caused the crash?

ABCNEWS’ John Nance at 2:56pm ET

We don't have any firm indication at this point that would justify saying that one particular thing was a primary cause. But it is a very tantalizing element that a pilot observed flame coming from one of the left engines in a way that simply is not routine in a Concorde takeoff. This, followed by the accident itself, is a very strong indication of engine loss on takeoff at the most critical point in the Concorde's flight.

In addition, since the Concorde can continue takeoff successfully, in most circumstances, on three engines of its four, and since all Concorde pilots are well trained to handle single engine loss on takeoff, there is reason to believe that we may have had a two-engine failure, which would explain in many ways the inability of the aircraft to sustain flight.

What could happen in such a situation is an inability to climb, and deteriorating airspeed, leading to a loss of directional control as the thrust on the remaining engines causes the airplane to roll over.

Wang at 2:59pm ET

Could Mr. Nance address the issue regarding the fractures on the planes? I would like more information as to how important cracks on the wings are. It seems many older planes have this "problem." How could this contribute to what appears to be an engine problem?

ABCNEWS’ John Nance at 3:00pm ET

More than likely, the fractures in the wing structure reported by British Air a couple of days ago will play no role in this accident. However, the old tried-and-true caveat from the NTSB, "rule nothing in, rule nothing out," definitely applies at this stage. It does not appear to me to be a potential factor in an accident in which the wing was not observed to fail. But the engines are highly suspect.

Aging aircraft structures will always develop cracks. The problem is not the presence of cracks, but where they are and how deep they run. In this case, British Air indicated the fractures were structurally insignificant.