Two further variants were designed; the "PR Mk 6" was an unarmed photo reconnaissance variant. However, it was a short-lived program due to ever-present reheat problems. The last variant was the "F Mk 7"; this model was the first Swift variant to be fitted with guided missiles, having been armed with the Fairey Fireflash air-to-air missile and was powered by a new model of the Avon engine. Only fourteen F 7 aircraft were built and none of these ever entered service with the RAF, being relegated – along with its prototype missiles – to conducting guided-missile trials duties only.