As wildfires rage in California, the world's largest aerial firefighting tanker in the shape of a modified Boeing 747 passenger jet has flown in to help extinguish the flames — if it can get off the ground that is.

The converted jumbo jet, known as the B747-400 SuperTanker, has been fitted with large tanks capable of dropping 20,000 gallons (90,901 litres) of water or fire retardant foam or gel in 12 seconds – almost double the capacity of the next largest aerial tanker.

"We can lay lines down that are extremely long... that might take other tankers five to seven drops to do," Captain Tom Parsons of the Global SuperTanker Services was quoted by local California news outlet ABC7.

Despite being the same size as a commercial jet the Global SuperTanker can operate without any speed, altitude or operational restriction and claims to be unmatched by any other military or civilian tanker for performance.

With a top speed of 600mph it can reach almost any location in North America in around 4.5 hours from its Colorado Springs base and still offers crew comfort with 14 first class seats still remaining on-board.

Eleven out-of-control blazes have raged along Highway 49, endangering the 2,000 residents of the town of Mariposa, Sierra Nevada, as well as threatening Yosemite National Park. Now the Detwiler fire, which has ravaged an area of over 48,000 acres (19,424 hectares), could find itself assailed by this giant aerial craft to help contain it.

However, at the moment the SuperTanker sits on the tarmac as it awaits approval from the US Forest Service Interagency Air Tanker Board, according to the report. It is said tests on the tanking system require adjustment to deliver its retardant to a satisfactory manner. The SuperTanker has been used effectively internationally, including helping fires in Israel in 2016, but needs IAB approval in the States.

Should the SuperTanker actually get airborne the US Forest Service is said to have imposed tanker capacity at 5,000 gallons (22,730 litres), which will come as a further frustration.