affiliate in sinai has the intent to attack commercial aircraft. they've stockpiled shoulder-fired surface-to-air missiles as seen in these training videos. but experts say those missiles can't reach that high. >> we're talking maximum between 10,000 and 15,000 feet. maybe if you stretch on a really good hail mary maybe 20,000 feet. but 30,000 feet is not practical. >> this military analyst says the russian made buk missile system which brought down the malaysia's plane last year. but requires more manpower and training than that isis affiliate likely has. >> you have a control vehicle and another vehicle which controls extra missiles. >> wub theory investigators will likely pursue, did a terrorist sneak a bomb onboard? airline safety experts say there are ways other than terrorism that a passenger plane can break up at altitude. >> improper maintenance including a failure to detect and correct corrosion or an improperly done repair, or we've