The US has deployed manned and unmanned surveillance aircraft over the area.
Other EU countries have responded to the call for help with two fixed-wing aircraft and three patrol vessels.
The Oman deal is part of a government effort to sell 100 aircraft to the Gulf region in 2013, sales which could be worth more than £6bn to UK firms, Downing Street said in a statement.
The deal will safeguard jobs at BAE factories in Lancashire and Yorkshire, and small companies throughout the UK that support production of the aircraft, he added.
Initial assessments found the airstrip sustained "minor to light" damage, and is open to medical emergency aircraft but not public flights.
Although Iran had developed its own version of the missile system – unveiled for the first time last year – delivery of the S-300s will markedly upgrade its anti-aircraft missile defences at a time of increased tension in the region.
On 18 July, just hours after the MH17 crash, Abbott said: "Some years ago now, an American warship by mistake downed an Iranian aircraft.
None of his three allies reacted, although a bewildered Mr Dos Santos - whose forces are fighting with tanks, artillery and aircraft for Mr Kabila - said he thought the discussion was about a ceasefire.
Electronic warfare, cyber attacks, small groups of commandos and special forces will take the place of traditional army units, just as pilotless drones will take the place of conventional aircraft.
In other words: we do not, as yet, have an adequate response mechanism, an ability to eliminate the threat of terrorism the way decisive steps undertaken by the British SAS, the German GSG-9 and other units succeeded in reducing the number of cases involving hijacked aircraft to almost nil.
Buck faced a maximum of two years in prison and a £5,000 fine for being drunk on an aircraft.
