Saudi Arabia is buying 72 Eurofighter Typhoon jets from the UK in a deal that could be worth more than £6bn.
The Eurofighter is fully loaded and ready to take on its rivals in the sky
The order is a huge boost to BAE Systems, and is the latest development in a saga that has lasted more than two decades.
Why is this defence order so important to the UK?
The entire project has come in for huge criticism and the Eurofighter has had to fight off ferocious competition from the US and France to win export orders.
The Saudi deal is proof that Eurofighter can win large orders in a tough market. BAE Systems is one of the four main contractors building Eurofighter, with partners in Germany, Italy and Spain.
Thousands of high-tech jobs in Lancashire, where BAE Systems has its military aircraft division, will be safeguarded by the order.
The area is home to dozens of small specialist engineering companies that supply parts and expertise to the BAE Systems plant at Warton, just outside of Preston.
When the UK sold Tornado fighters to the Saudi air force in the 1980s, subsequent contracts for support and airfield infrastructure generated massive business for other UK companies in the defence and construction sectors.
The Eurofighter order may herald a similar bonanza for UK companies.
So who else is buying the planes?
Eurofighter's first export success was a small order from Austria for 18 aircraft. But the company subsequently lost out in a competition to supply jets to the Singapore Air Force, fanning fears that it would struggle to sell.
Now the huge Saudi order means other customers will feel more confident about buying the aircraft.
Norway, Greece and Turkey are all being mentioned as possible future customers for the Eurofighter.
Why has the Eurofighter been so controversial?
The aircraft was conceived during the 1980s as a counter to the latest Russian fighters, but technical challenges and the end of the Cold War led to calls for its cancellation.
As a result, the testing programme was delayed and the first prototype did not fly until 1994.
Costs rose dramatically during the project and the UK's bill for buying 232 has soared from £7bn to an estimated £15bn.
Critics argue that the UK's Royal Air Force (RAF) and its European allies no longer need a top of the range fighter.
They point out that conflicts in Iraq and Afghanistan require infantry and helicopters, not sophisticated fighter jets that will take up a huge chunk of the hard-pressed defence budget.
Also, the RAF has struggled to get the aircraft into service and the initial deployment with the air forces of the four partner nations was repeatedly delayed.
So why is the UK pushing ahead with the Eurofighter?
Simply put, because the four partner nations need a fighter to replace existing aircraft.
The RAF must replace aging Tornado F3 fighters, which defend UK airspace, and elderly Jaguar fighter-bombers, which support the army. These aircraft were designed in the 1960s and 1970s and have been in service for 20-35 years.
And while the military threat from the Soviet Union no longer exists, Russia is selling its top-of-the-range fighters to many countries.
At the same time, China is increasing its presence in the international fighter export market.
So is the Eurofighter any good?
Critics have suggested that the Eurofighter is only useful for air-to-air combat, and not for supporting troops on the ground.
And they have complained that it was not designed to evade radar, like the latest generation of US stealth fighters.
In fact the Eurofighter was designed from outset to be a fighter-bomber that could switch from dog-fighting in the air to attacking targets on the ground all during the same mission.
Some observers have claimed that many criticisms of the fighter plane have come from US aerospace companies alarmed at the prospect of losing customers to the Eurofighter.
Also, designing a fighter to be stealthy can sometimes mean tradeoffs when it comes to manoeuvring performance.
What makes it special?
The Eurofighter's engines, made by Rolls-Royce, give enormous power in relation to the aircraft's weight.
The fighter jet is controlled by computers that feed instructions into the wings and tail far faster than a human pilot could manage, allowing the pilot to throw the plane around the sky and use entirely new tactics.
So what will be the Eurofighter's main competition?
The Joint Strike Fighter (JSF), which the US is developing in co-operation with the UK, is due to enter service after 2012.
But this project has hit serious technical problems and is under threat in the US Congress.
The US Air Force has already begun to take delivery of another superjet, the F-22 Raptor.
This is very stealthy but costs twice the price of the Eurofighter, and reports suggest that RAF's Eurofighters have flown highly successful missions against the F-22 during recent exercises in the US.
It also is competing with the French-made Rafale, which is very similar to the Eurofighter and may be on the UK's Royal Navy shopping list.