In the next stage of the steadily rising stakes in the Balkan war, Invincible will play a key role in imposing a blockade to restrict Yugoslavia's oil supplies. Her Sea King helicopters will be Nato's eyes and ears in tracking any ships that try to take oil to Montenegro, Serbia's fellow Yugoslav republic and its outlet to the sea.
This could bring her into conflict with Russian ships. Captain James Burnell-Nugent is acutely aware that any boarding of a Russian vessel would be as much a political decision as a military one. However, he says, if the need arises he will be ready.
In the meantime, the pilots on board the aircraft carrier are already flying to the limit of their operational capability every night. The flights, which last up to five and a half hours in darkness, including taking off and returning to the craft, are hazardous as well as taxing. The pilots are reporting a steady increase in Serbian anti-aircraft fire and increasing levels of combativeness by their missile defences.
A senior pilot, who has flown every night for the past two weeks in missions over Kosovo and Serbia, and has also been at sea for seven months, said: "It's exhausting, but it is getting very interesting. We are getting quite serious anti-aircraft fire, and I am finding now that Serbian missile defences are locking on to us. You can see the red laser dots, and you know you are in their sight. Then they switch off. They are saving themselves. They are gauging us, just as we are gauging them. Obviously this is something for the future."
Among many in the ship's crew there is a feeling that the conflict is "a just war". Repeatedly those on board stressed their frustration at not being able or allowed to help the Kosovars in refugee camps just a short flight away.
One helicopter pilot said: "If we are not being used operationally, we'd much rather be in Albania trying to move the refugees, or using our expertise to build camps, putting in sanitation, or just loading trucks."
Two young pilots, Ian Sharrocks and Andy Watson, both joined up on the same day five years ago. They now find themselves about to face their first war together. Lieutenant Sharrocks, 24, wears a badge on his flying suit saying "Nato Tigers - Hard to be Humble".
The main concern for him and Lieutenant Watson is how they can help the refugees: "We can strip down our machine and carry out 30 people at a time. We are heavily armed for combat, but we are also very, very keen to do what we can for the refugees."
Lieutenant Watson agrees with him: "We know what it's like in the camps, and it's not just a wish - we feel a need so deeply to help these people."
Invincible carries sailors, airmen and Royal Marines. Some of the Marines say they know a little of what is going on inside Kosovo. One crew member said: "The reports we are getting are so horrific, so terrible, that even I, someone who has seen some dreadful things in my time, find it difficult to comprehend.
"I've spoken to people who have been inside Kosovo, I do not want to say in what capacity, but the butchery there is frightening. We are dealing with a bunch of fascists. No one now believes there will not be a land war.
"It is simply not true that the politicians were told that this war can be won by air strikes alone. The terrain makes that impossible.
"You need troops to gain ground and hold ground. That's what we shall have to do, albeit belatedly."