GKN Aerospace said crews are working to stabilize a chemical tank at its aircraft transparencies plant in Garden Grove, California, after the overheated storage tank containing methyl methacrylate created a potential explosion risk and forced evacuations around the site.
The incident occurred at GKN Aerospace Transparency Systems, a Southern California facility that makes cockpit windows, canopies and windshields for military and commercial aircraft. The site also makes specialty aerospace plastics. The facility employs about 500 people.
GKN Aerospace said the company is working with local officials, emergency responders and technical specialists as response operations continue. Melrose Industries, GKN Aerospace’s UK-listed parent company, said GKN is also working with customers on contingency plans.
Emergency crews responded after a thermal issue was identified on May 21, 2026, in a tank holding methyl methacrylate, a flammable chemical used in plastics manufacturing. Officials warned that the tank could rupture and spill up to 7,000 gallons of material or explode, potentially affecting other tanks at the GKN site.
A crack in the tank later relieved pressure, easing fears of a catastrophic explosion. On May 26 that about 16,000 people who live closest to the plant still could not return home, although most of the roughly 50,000 people initially evacuated had been allowed back after the risk declined.
Authorities said the situation had improved but had not fully ended. Crews worked overnight to neutralize two nearby tanks and prevent them from being affected by the compromised tank.
Fire crews stopped spraying cooling water directly on the tank after its internal temperature stabilized at 92 degrees Fahrenheit, down from about 100 degrees over the weekend, while the plant’s sprinkler system continued cooling the tank.
Health officials said they had not detected contamination or fumes. Orange County Health Director Regina Chinsio-Kwong said at a May 25 news conference that there was “not a leak.” GKN Aerospace said its priority remained the safe resolution of the incident so residents could return home as quickly as possible.
The incident weighed on Melrose shares on May 26 as the company’s share prices fell as much as 7% in London trading, making Melrose the biggest loser on the FTSE 100 and pan-European STOXX 600 indexes at that time.
Melrose did not disclose a financial impact from the incident or say whether insurance would cover any costs.
Environmental monitoring is expected to continue after the emergency response. AP reported that the South Coast Air Quality Management District will monitor air quality for several months, while the US Environmental Protection Agency will check sewer and storm drains for possible spills.
The incident also comes after prior regulatory scrutiny at the site. AP reported that GKN Aerospace agreed in 2025 to pay more than $900,000 to settle South Coast Air Quality Management District violations involving recordkeeping, permitting issues and nitrogen oxide emissions.