A Southwest Airlines passenger flight in April came within 400 feet (120 meters) of slamming into the ocean off the coast of Hawaii after weather conditions forced pilots to bypass a landing attempt.

The Boeing 737 Max 8 jet briefly dropped at an abnormally high rate of more than 4,000 feet per minute before the flight crew pulled up to avoid disaster, according to a memo that Southwest distributed to pilots last week. No one was injured on the flight, which safely returned to its departure airport in Honolulu.

The U.S. Federal Aviation Administration said it was investigating the incident.