Government officials are investigating an incident in Dallas skies involving three planes.

The Federal Aviation Administration (FAA) is conducting an investigation regarding three planes that circled the Dallas area while a wave of severe storms persisted across the region on March 16, as previously reported by The Dallas Express.

The FAA told WFAA in a statement that this incident involved Boeing 747 UPS Flight 5510, Boeing 767 FedEx Flight 3952, and Boeing 737 United Airlines Flight 2319.

Pilots on the FedEx aircraft received an alert from the onboard Traffic Collision Avoidance System (TCAS) due to the proximity of the UPS aircraft and descended into the 1,000-foot vertical safety buffer between it and the United Airlines aircraft.

The event was described as a “loss of standard separation.” Loss of standard separation occurs when the minimum horizontal and vertical distances between aircraft are compromised, which can result in a midair collision.

The alerts these three aircraft received during the incident notified the pilots of conflicting flight paths, not an imminent collision.

The FAA requires that “above FL 290 (flight level), no aircraft should come closer than 2,000 feet except in airspace where Reduced Vertical Separation Minima (RVSM) can be applied in which case the vertical separation is reduced to 1,000 feet.”

The FAA also told WFAA that the agency’s preliminary analysis indicated a distance of 1.1 miles laterally and 900 feet vertically between the FedEx aircraft and the UPS aircraft and a distance of 1.3 miles laterally and 1,000 feet vertically between the FedEx and United Airlines crafts at their closest approaches.

The flights were delayed but later landed safely at Dallas-Fort Worth International Airport, according to NBC 5 DFW.

The FAA issued a notice to pilots, airlines, and other related entities on March 22, urging that they take “key safety actions” following the most recent safety summit. The agency urged that associated entities adhere to policies on checklists, air traffic control instructions, and company procedures.