US investigators are examining the thrust-reverser system of the Southwest Airlines Boeing 737-700 that crashed at Chicago Midway on Friday after the captain told them the system did not appear to operate correctly.

SW737-300

At a press conference in Chciago, the NTSB said the captain reported a delay in the reversers deploying after he selected them, although the system did then operate.

After speaking to flight attendants on the aircraft, investigator Robert Benzon said: "They all said it was a smooth landing but they could sense a lack of deceleration."

The 16 month-old aircraft, N471, ran off the end of the 6,520ft (1,988m)-long runway 31C and onto a road killing a six year-old boy in a car after landing in a night-time snowstorm.

Southwest said: "The aircraft was released from the airline’s Phoenix maintenance facility on December 7, 2005. There were no indications that the aircraft was experiencing any type of maintenance problems.”

The 737-700, was operating as flight 1248 from Baltimore/Washington. It was due to have landed at Chicago Midway at 18:30 but circled the airport before landing at around 19:15, says Southwest. Snow was falling at the time.

On landing the aircraft “veered off the runway…onto Central and 55th Ave”, says Southwest. Reports say this intersection is just past the northwest corner of the airport.

Several reports say the aircraft landed on runway 31C. This is the longest runway at the airport, at around 6,520ft (1,988m).

Southwest says the captain who operated flight 1248 has been flying with it for 10 years while the first officer has been flying with it for more than two years.

Source: Flight International