It's not like the plane was going mach 2 or outside the range of the stinger. Yes, it was at the limits, but definitely still within range. Also, I'm not sure that what the witnesses may have seen was some sort of flash coming off the aircraft after it exploded, and being confused later as to whether it was going up or down. Nighttime, relflections off the water, and big flashes of light can and will confuse any eyewitness. Therefore, my opinion is, if it were an attack, either an explosion on board the aircraft or very possibly a smaller plane flying into it.