The Global SuperTanker
N744ST, Spirit of John Muir, carried 19,600 US gallons of retardant and fought fires on four continents before shutting down in 2021.
The Evergreen Supertanker proved a 747 could fight fires. The Global SuperTanker was the version that did it properly, on a modern airframe — and it is the largest firefighting aircraft ever flown.
The aircraft
N744ST, tanker number 944, a Boeing 747-400 named Spirit of John Muir.
It was rated to carry up to 19,600 US gallons (74,000 litres) of fire retardant or water — a payload no other aerial tanker has approached.
How it came about
Global SuperTanker Services acquired most of Evergreen’s assets when that company failed, including the intellectual property and the pressurised drop system. The plan was straightforward: take a proven firefighting installation off an ageing 747-100 and put it into a far more capable and efficient 747-400.
The aircraft was certified for firefighting by the FAA in September 2016.
Where it worked
It fought fires on four continents in five years:
- Chile and Israel, early in its career
- California, under contract to US authorities during the 2017 wildfire season
- Bolivia, in August 2019
The pressurised system meant it could drop at altitude and at varying flow rates, rather than simply dumping a load — laying a retardant line rather than making a single splash.
Why it stopped
Not because it did not work. Global SuperTanker Services ran into financial difficulty and shut down in April 2021.
The economics of a very large air tanker are awkward: it is enormously capable on the worst days and enormously expensive on all the others, and fire agencies contract by the season rather than by the emergency. A fleet of smaller tankers flying more sorties has usually won that argument.
The aircraft was sold to National Airlines and converted back to a freighter in 2021 — still wearing its tanker paint as recently as 2025.
What replaced it
Nothing of the same size. The large-volume tanker concept passed to Boeing 737-derived Coulson tankers, which carry far less but cost far less to keep on standby.
The 747 remains the largest firefighting aircraft ever to have flown, and given that the production line closed in 2023 it is likely to keep that record.
Related
Frequently asked questions
- What was the largest firefighting aircraft ever built?
- The Global SuperTanker, a converted Boeing 747-400 rated to carry up to 19,600 US gallons (74,000 litres) of fire retardant or water. It operated from 2016 until the company shut down in 2021.
More in Special Boeing 747s
Special Boeing 747s
The 747s built for jobs no airliner does — Air Force One, the Dreamlifter, the Shuttle Carrier, a flying observatory, a firefighting tanker and an airborne laser.
The 747 ASB
Boeing's 1986 answer to the Airbus A340 and MD-11 — a shortened 747 with 747-400 technology. It was never built.
The 747 CMCA
A proposed USAF Boeing 747 armed with up to 72 cruise missiles on rotary launchers, studied during B-1 development. It was never built.
The Boeing Dreamlifter
Four 747-400s rebuilt with a swollen fuselage and a swing tail to carry Boeing 787 wings and fuselage barrels between factories.
The 747 as a flying testbed
General Electric, Rolls-Royce and Pratt & Whitney all fly engines on 747s — because a four-engined aircraft can carry a strange engine safely.
SOFIA — the flying observatory
A former airline 747SP carrying a 2.5 m infrared telescope, flying above the water vapour that blocks infrared light from the ground. Retired 2022.