W8951 - Incident: Cargojet B762 at Mexico City on May 2nd 2022

A Cargojet Boeing 767-200, registration C-FHCJ performing flight W8-951 from Mexico City (Mexico) to Cincinnati,KY (USA) with 4 crew, was climbing through FL290 out of Mexico City when the crew heard a loud thud noise from the main cargo compartment and felt a pressure bump in their ears. The flight crew noticed the cabin altitude was climbing at more than 1000 fpm and went above 10,000 feet, the cabin altitude light and horn activated. The crew donned their oxygen masks, declared PAN PAN and requested an immediate descent. Initial clearance was to descend to FL200, while descending the crew checked their minimum safe altitude as they were flying over mountaineous terrain in night conditions. The crew decided to return to Mexico City, worked the checklists, could not regain control of the cabin pressurization even in manual control. While on approach descending below 10,000 feet the crew removed the oxygen masks, were vectored for the approach to runway 23L being number 2 in the approach sequence. While on short final tower advised of a late landing clearance as the preceding aircraft had not yet vacated the runway, that aircraft for some reason decided to vacate at the very end of the runway, upon reaching the decision height there still was no landing clearance and the first officer was unable to get a word in on the tower frequency forcing the Cargojet crew to go around, landing clearance was issued only when the aircraft was well in the go around already. As result of the go around the aircraft needed to climb to 12000 feet which again triggered the altitude warning and altitude horn, the crew again donned their oxygen masks. The aircraft subsequently landed safely on runway 23L about 15 minutes after the go around and 75 minutes after departure.

The aircraft remained on the ground for about 5.5 hours, then departed again.

The Canadian TSB rated the occurrence a reportable incident but did not elaborate on the cause of the loss of cabin pressure.