Boeing 747 Supertanker

What is the 747 Supertanker?

The 747 Supertanker is a Boeing 747 jumbo jet converted into a wildfire air tanker. It is the largest aerial firefighting aircraft ever built.

It was rated to carry up to 19,600 US gallons (74,000 L) of fire retardant or water. The specification table for the aircraft is on this page.

How the Supertanker was developed

The idea grew out of the 2002 fire season. Two fatal air tanker crashes, a C-130 Hercules and a PB4Y-2 Privateer, led the US Department of Interior to ask industry for new options.

Evergreen International Aviation proposed converting 747 freighters. The first converted aircraft, N470EV, flew on February 19, 2004. It was a 747-200 and never entered service.

The FAA issued a supplementary type certificate in October 2006, after Evergreen had spent about $40 million on the program.

The two aircraft that fought fires

Only two Supertankers ever flew firefighting missions. Both were first-generation conversions of airliners that had served other airlines.

Tanker 979 (N479EV) was a 747-100 built in 1971 for Delta Air Lines. It entered service in 2009 with a fire in Cuenca, Spain, and made its first US drop on August 31, 2009, at the Oak Glen Fire. It was intentionally destroyed for salvage on July 12, 2017.

Tanker 944 (N744ST), nicknamed Spirit of John Muir, was a 747-400 that previously flew for Japan Airlines. Global SuperTanker Services bought Evergreen’s assets in August 2015 and moved the 747-100’s tank system into this airframe. The FAA certified it in September 2016.

How the tank system worked

The Supertanker used a pressurized liquid drop system. The crew could release retardant at high pressure or at a gentler rate, close to the speed of falling rain.

It dropped from 400 to 800 feet above the ground at about 140 knots. Its operator claimed a drop pattern up to 3 miles long and 150 feet wide.

The aircraft needed a runway of about 8,000 feet. That limited it to major airports, which are often far from the fire.

Where the Supertanker flew

The Supertanker worked fires on several continents. Missions included the Mount Carmel fire in Israel in December 2010, the Wallow Fire in Arizona in June 2011 and fires near Haifa in November 2016.

In January 2017 it flew in southern Chile. In late 2017 it was leased by Cal Fire, mostly over the Thomas Fire, and in November 2018 it worked the Camp Fire in Butte County, California.

The Global SuperTanker was often based at Colorado Springs, from where it could reach most of the US in around five hours.

Why the Supertanker stopped flying

Evergreen collapsed first. It shut down on November 30, 2013, and filed for Chapter 7 bankruptcy a month later. Its 747 airframes were sold to Jet Midwest Aviation.

Global SuperTanker kept the idea alive with the 747-400. In April 2020 the National Interagency Aviation Committee again declined to approve its retardant delivery system. It cited coverage level, retardant retention, trail-off outside the drop zone and inconsistent flight profiles.

In April 2021 the owners decided to cease operations. Operating costs were reported at up to $250,000 per day. The aircraft was sold to National Airlines, which converted it back to a freighter and registered it N936CA.

Explaining the numbers

The panel on this page is a single set of figures for a program that used three different 747 models. The two aircraft that fought fires were a 747-100 and a 747-400, so treat the dimensions and weights as typical of the 747 family rather than exact for one tanker.

The 19,600 US gallon rating is the type’s headline capacity. Reporting in 2021 said the 747-400 system was trimmed from an original 20,000 gallons to 17,500 gallons in practice.

Frequently Asked Questions

What is the biggest tanker plane?

The 747 Supertanker was the largest aerial firefighting aircraft ever built. It was rated for up to 19,600 US gallons (74,000 L) of retardant or water.

Is the 747 Supertanker still flying?

Not as a firefighter. Global SuperTanker ceased operations in April 2021 and sold the 747-400 to National Airlines for freight use.

How many 747 Supertankers were there?

Three airframes were converted by Evergreen or Global SuperTanker, but only two, a 747-100 and a 747-400, fought fires. The 747-200 prototype never entered service.

Who built the 747 Supertanker?

Evergreen International Aviation converted the first aircraft and later Global SuperTanker Services reworked the 747-400, using the tank system from the earlier tanker.

What is the registration N744ST?

N744ST was the Global SuperTanker 747-400, Tanker 944. After the 2021 sale it was re-registered N936CA.