MPs have overwhelmingly backed UK air strikes against so-called Islamic State in Syria, by 397 votes to 223, after an impassioned 10-hour Commons debate.
Four Tornado jets took off from RAF Akrotiri, Cyprus, after the vote. Their destination has not been confirmed.
A total of 66 Labour MPs sided with the government as David Cameron secured a larger than expected Commons majority.
The PM said they had "taken the right decision to keep the country safe" but opponents said the move was a mistake.
A further four fighter jets remain on standby at the air base, which is used for bombing missions to Iraq and from where reports have suggested air strikes against IS targets in Syria could also be launched.
Two of the four Tornados landed back in Cyprus just over three hours later, shortly before 03:00 GMT.
BBC defence correspondent Jonathan Beale said they had left RAF Akrotiri with three 500lb Paveway bombs each and returned to base without those weapons.
The Ministry of Defence is expected to give details of their targets later on Thursday, he added.