Remembering Pan Am Flight 160—50 Years Later

Posted on 11/6/2023 by Nick Waldron

November 3, 2023 marked the 50th anniversary of one of the most impactful hazmat disasters in history. Pan Am Flight 160 (call sign: "Clipper 160"), a cargo flight headed to Frankfurt, Germany from JFK Airport in New York City, crashed—likely because of improperly packaged hazardous materials.

Not long after departing from JFK on November 3, 1973, the three-man flight crew of Clipper 160 reported smoke in the electronic equipment center situated under the cockpit. The crew planned to make a landing in Boston, but were granted a landing back at JFK. Then the cockpit filled with thick smoke, changing the landing plan back to Boston.

The smoke became so thick that the crew lost control of the plane. Loaded with 52,912 lbs. of cargo including 15,360 lbs. of chemicals, the aircraft struck the ground nose-down less than one hundred yards from the end of the approved runway. No one on board survived.

A plane landing at Boston Logan International Airport.

The National Transportation Safety Board (NTSB) could not determine the cause of the “continuously generated and uncontrollable” smoke, but the Board believes that nitric acid leaked and reacted with sawdust it was packed in.

A “general lack of compliance” with the then-current regulations is believed to be a contributing factor, and that lack of compliance, NTSB claimed, “resulted from the complexity of the regulations, the industry wide lack of familiarity with the regulations at the working level, the over-lapping jurisdictions, and the inadequacy of government surveillance.”

In early 1975, the New York Times reported:

WASHINGTON, Feb. 24—The fatal crash of a Pan American World Airways cargo jet at Boston in November, 1973, was attributed today to inadequate regulations for the air shipment of hazardous materials and lax enforcement by the company and the Federal Aviation Administration of existing regulations.

The National Transportation Safety Board said that this laxity permitted improperly packaged nitric acid and other hazardous materials to be placed on board Clipper 160 without the knowledge of the crew.  

New York Times, February 25, 1975

Reproducing the Hazmat Reaction

The Board’s accident report includes testing done to recreate the reaction of nitric acid improperly packed in saw dust—the situation that is believed to cause the smoke that filled the cockpit of Flight 160.

From the report, pages 14 and 15:

Test of Leaking Nitric Acid

Numerous hazardous materials on Clipper 160 had not been packaged according to regulations. Nitric acid was one. [The regulations require] nitric acid bottles ‘be placed in tightly closed metal containers, and well cushioned therein on all side with incombustible mineral packing material…The metal container must be packed in outside containers and well cushioned by incombustible mineral packing material as described in this section.’

The nitric acid bottles were found packed in marked wooden boxes and were cushioned by sawdust. There were no inside metal containers. On November 13, 1973, tests were conducted to determine the effects of leaking nitric acid.

Tests conditions:

  • Wind Velocity 11kn.
    Temperature 54°F.
    Dew Point 31°F.

Packing materials recovered were air-dried. The packing material was then used to repack a bottle of nitric acid. The bottle cap was in place, but completely loose—no threads were engaged.

The box into which the bottle had been packed was then inverted, and the time recorded as 0:00 minutes. The following observations were made:

7 min: Bluish-white smoke was observed from around the lower surface on the container.
11 min: The smoke downwind had an odor similar to that of burning wood.
13 min: The white smoke flared profusely around the box and was orange momentarily.
15 min: The quantity of smoke reduced.
17 min: The odor of the smoke was similar to that of burning wood.
19 ½ min: Flames were visible near the bottom of the box.
21 ½ min: Flames penetrated the top of the container.

The ground on all sides of the nitric acid box was sooted heavily.

Response to the 1973 Disaster

NTSB made 16 safety recommendations following its investigation of the incident—the first, on November 29, 1973, and the last on October 1, 1974.

The President of the United States signed the Hazardous Materials Transportation Act of 1975 into law less than two years after the incident on January 3, 1975. On this anniversary we remember the three crewmembers of Pan Am Flight 160. This tragic loss reminds us of the importance of the safe and compliant shipment of hazardous materials.

Tags: hazardous materials, hazmat history

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