The U.S. National Transportation Safety Board said on Sunday, Nov. 2 it is sending a team to investigate an Oct. 29 close call between a Southwest Airlines jet and a medical helicopter near Cleveland Hopkins International Airport in Ohio.

The NTSB said the two aircraft experienced a loss of separation – meaning they came closer to each other than the required minimum safe distance – when Southwest Flight 1333 was making its final approach on a flight from Baltimore-Washington International Thurgood Marshall Airport (BWI).

This prompted the Southwest pilot to abort the landing. Southwest said the Boeing 737 landed safely a short time later.

The NTSB and Southwest did not disclose the number of passengers and crew aboard the airliner. The helicopter appears to have been transporting a patient at the time of the incident, based on how it was identifying itself at the time.

Southwest said in a statement on Sunday, Nov. 2 it "appreciates the professionalism of our crew in responding to the situation. We are engaged with the National Transportation Safety Board and will support the investigation."