BBC NewsBritish Tornado jets have returned to RAF Akrotiri in Cyprus after carrying out a fifth combat sortie over Iraq.
The pair returned to RAF Akrotiri in Cyprus, and BBC defence correspondent Jonathan Beale said there were “no reports of any weapons dropped”.
The first jets to take part in a mission against Islamic State (IS) militants had carried out armed reconnaissance missions at the weekend.
Parliament voted by 524 votes to 43 to take action against IS in Iraq.
IS – also known as Isis or Isil – controls large swathes of Syria and Iraq after rapid advances through the region in the summer. It has been using the Syrian city of Raqqa as the capital of its self-declared caliphate.
The most recent clashes have taken place around a key town near the Iraqi capital Baghdad but Iraqi ground forces, backed by US-led air strikes, appear to have halted the advance of IS.
The BBC’s Lyse Doucet in Baghdad said there was growing concern that the militants were getting dangerously close to the capital.
‘Comprehensive strategy’
RAF Tornados have been flying reconnaissance missions over Iraq for the past six weeks, but the five sorties in recent days have been the first flights since they were authorised to launch air strikes.
The Tornados, loaded with laser-guided bombs and missiles, have been supported by a Voyager air-to-air refuelling aircraft.
Analysis
BBC defence correspondent Jonathan Beale, at RAF Akrotiri, Cyprus
RAF Tornados have been returning to Cyprus with all their weapons. The obvious question is why?
For one thing, they’re not targeting a conventional military. There is unlikely to be a list of ammo dumps or barracks to hit, as there was during the intervention in Libya.
Also, they’re more likely to be looking for targets of opportunity such as IS fighters and vehicles on the move. That might require hours of surveillance.
And RAF crews will be operating under strict rules of engagement. They’ll have to be certain before they fire any weapons. They can’t hit the civilians they are there to protect.
IS fighters will also have had time to adapt. Their fighters will now be well aware of what’s going on above.
The RAF’s contribution is limited too. The US is flying dozens of sorties a day with hundreds of hours in the air.
And US missions are not just limited to Iraq – unlike the RAF, they’re able to target the extremists in Syria too.
Defence Secretary Michael Fallon has warned such operations could continue for weeks or months.
He told BBC Radio 4’s The World this Weekend: “This is not a weekend campaign. This is going to take a long time.”
Prime Minister David Cameron has insisted there is a “comprehensive strategy” in place for defeating IS.
Meanwhile, US President Barack Obama has acknowledged that the United States underestimated the threat posed by the militants.
The US has been carrying out air strikes in northern Iraq since mid-August, and has been supported by the French since last week.
About 40 countries in total, including several from the Middle East, have joined the US in taking action against IS.