Date: 201306
Local time of day: 1801-2400
Location: MDW.Airport, IL
Flight conditions: VMC
Light: Daylight
Aircraft: B737-700
Operator: Air Carrier
Operating under: Part 121
Flight plan: IFR
Flight phase: Takeoff / Launch
ATC / advisory: Tower MDW
Second aircraft: Any Unknown or Unlisted Aircraft Manufacturer
Reporter organization: Air Carrier
Reporter function: First Officer
Human factors: Communication Breakdown
Second reporter function: Captain
Anomaly: ATC Issue All Types; Conflict Ground Conflict; Less Severe; Deviation / Discrepancy - Procedural Clearance
Detector: Person Flight Crew
When detected: In-flight
Result: Flight Crew Executed Go Around / Missed Approach
Contributing factors: Airport; Human Factors
Primary problem: Human Factors

Narrative: MDW was busy like usual around this time. Traffic continually landing 4R. On pushback; we were asked if we wanted 31C. Said yes. We were cleared to lineup and wait 31C. We acknowledged and then lined up. Then we were cleared for takeoff. I read this back verbatim; 'Heading 250 cleared for takeoff 31C Company Flight Number.' But; I think ATC MEANT to clear holding traffic on 4R for takeoff instead. Anyway; an aircraft had to go-around on 4R shortly after we started our takeoff roll.


Second narrative: Departing MDW primary runway in use was 4R. Ground asked if we could accept 31C. We advised we were able 31C. After all required checklists completed; we were cleared to line up and wait 31C. There were several aircraft on final for 4R. Tower then cleared Company aircraft to line up and wait on 4R. As traffic cleared 4R; Tower cleared us; 'Company Flight Number; cleared for takeoff. No delay.' Without delay we began our takeoff roll. At about 80 knots; I heard Tower and Company aircraft on 4R discussing who was cleared for takeoff. Tower instructed an aircraft on final for 4R to go-around. We continued as my outside scan indicated no threats. Tower then repeated; 'Company Flight Number; cleared for takeoff.' Takeoff and climbout were normal and uneventful. Upon reflection; it is apparent that the Tower Controller cleared our aircraft for takeoff on 31C when he meant to clear Company aircraft for takeoff on 4R. Tower Controller seemed briefly unaware of what he had done; but recovered nicely by acting quickly to instruct aircraft on final to go-around and to re-clear us for takeoff; so there was no confusion on our part. Tower definitely cleared us for takeoff and; as is often the case; without delay. Had I been aware of how close the aircraft on short final was to touch down (1.5 miles maybe?); I could have questioned the clearance. But; the controllers at MDW are so competent at multiple runway departures and traffic flow; we assumed he had time to clear us for takeoff and then clear Company for takeoff on a crossing runway with no problem. This was not a near-miss situation. It was just a Controller who cleared the wrong aircraft for takeoff but then responded appropriately to his mistake.


Synopsis: B737-700 flight crew read back the takeoff clearance and started their takeoff roll from Runway 31C at MDW; ATC directed an aircraft on final for Runway 4R to go-around. Flight crew suspected the takeoff clearance may have been intended for an aircraft lined up and awaiting clearance for takeoff from Runway 4R; thus precluding the use of the runway for the go-around aircraft.