Tornado crews flying over Iraq say their mission is 'personal' as they seek 'some sort of justice' for murdered RAF engineer David Haines.
The 44-year-old British aid worker, who served with the force for 12 years, was beheaded by ISIS militants in a shocking propaganda video after being taken hostage in Syria.
Now servicemen and women based in RAF Akrotiri in Cyprus - who have so far not unleashed firepower on any suitable targets in nothern Iraq - say they want to stop other captives suffering the same fate as their former colleague.
British hostages Alan Henning and John Cantlie are still being held under threat of execution by the same fighters.
David Haines, 44, a former RAF engineer, pictured, was murdered by ISIS militants in a horrific video after being taken hostage in Syria
Servicemen and women based in RAF Akrotiri in Cyprus say they want to stop other captives suffering the same fate as their former colleague
An RAF source told The Telegraph: 'Any human being would be horrified by what Isil is doing to British hostages and that applies as much to the RAF as to anyone.
'Add to that, one of their victims was a former RAF serviceman, and it definitely feels a bit personal for all of us here.
'It's not about revenge but perhaps some sort of justice – and certainly the hope that we can stop more people suffering the way David and other captives have.'
Their comments came as RAF jets flew armed sorties for a second day over Iraq yesterday – but again failed to locate any suitable targets for their weapons.
Defence chiefs insisted that the flights by Tornado GR4 fighter-bombers were invaluable for gathering intelligence on the Islamist jihadists who have swept across large swathes of Iraq and Syria, carrying out massacres.
But the failure to unleash any firepower has fuelled concern that Britain is failing to pull its weight in the international coalition against Islamic State.
On a mission: The RAF jets seek out their terror targets - which they failed to find and bomb, again
Military commanders warned that Britain should brace itself to be dragged into a ground war in Iraq to crush IS, which is also known as Isis and Isil. Former top brass also warned that the air campaign would be futile unless the UK could target the terrorists in Syria.
A female fighter pilot led Britain's first combat mission against Islamic State.
The woman, who has not been named, flew one of the RAF Tornados on the perilous sortie over jihadist-held territory in northern Iraq on Saturday.
Stationed at RAF Akrotiri in Cyprus, she is believed to be a weapons systems operator.
She sits in the jet's rear seat and fires the aircraft's Brimstone and Storm Shadow missiles and Paveway IV bombs.
The airwoman, who serves with II (AC) Squadron, flies at exactly the same combat level as her male colleagues.
A Ministry of Defence source said: 'No one makes a big fuss of having a female pilot. We have females in aircrews and ground crews and they are here because of their abilities. Everyone is just doing their jobs.'
The involvement of a woman RAF pilot comes amid reports that the family of Major Mariam Al Mansouri of the United Arab Emirates, who flew an F-16 jet in bombing raids against positions in Syria last week, has disowned her.
While the Ministry of Defence confirmed that the RAF's third mission had – like on Saturday – failed to locate any targets, US-led coalition aircraft targeted four makeshift oil refineries under IS control in Syria, as well as a command centre.
The mobile refineries generate up to £1.2million a day for the militants.
On Friday, David Cameron won Parliament's backing for air attacks against fanatics in Iraq but, crucially, he stopped short of seeking permission to allow UK jets to bomb targets in Syria, where IS has its stronghold.
By contrast, the US and Arab nations – including Saudi Arabia, the UAE and Jordan – have sent their jets to bombard IS positions around the city of Raqqa, in northern Syria, where it is believed British hostages Alan Henning and John Cantlie are being held under threat of execution.
Lord Richards, who retired as head of the Armed Forces last year, was among a number of senior military figures who warned that the extremists could not be defeated by air attacks alone. He said Western governments had blundered by ruling out the deployment of ground troops and suggested a military campaign on the scale of the attacks that toppled Saddam Hussein in 2003 was needed to crush IS.
Then, a force of 380,000 troops – including 45,000 British service personnel – invaded Iraq.
Lord Richards said: 'How the hell can you win the war when most of your enemy can end up in a country you can't get involved in?'
He said Iraqi and Kurdish forces should be trained and armed to fight a ground war against the militants. But if they fail, the West should be prepared to send in troops.
'Ultimately, you need a land army to achieve the objectives we've set – all air will do is destroy elements of IS,' said Lord Richards. 'The only way to defeat IS is to take back land they are occupying, which means a conventional military operation.'
Major General Julian Thompson, a former commander in the Royal Marines who recaptured the Falklands, agreed that an air campaign by itself would not be enough.
Armed: A Tornado at RAF Akrotiri is loaded with a laser-guided bomb
'I think we should have forward air controllers to ensure that targeting is done properly.'
Lord Dannatt, a former Chief of the General Staff, said: 'Attacking Isil from the air solely above Iraq is dealing with half a problem, not all of it. The US has correctly concluded that carrying the fight against Isil into Syrian airspace is right – we may yet come to the same conclusion.'
Defence Secretary Michael Fallon warned that the RAF's mission – codenamed Operation Shader – could last years. 'This is not a weekend campaign,' he said. 'This is going to take a long time.'
Britain has deployed six two-seater Tornados, a refuelling aircraft and a spy plane from RAF Akrotiri in Cyprus. Airmen spoke yesterday of their mission against IS feeling 'personal' following the beheading of former RAF serviceman David Haines.
One ground crew member, who declined to be named amid security concerns, said: 'Any human being would be horrified by what IS is doing to British hostages. Add to that one of their victims was a former RAF serviceman and it definitely feels a bit personal for all of us here. It's not about revenge, but perhaps some sort of justice.'