The next two Lightning variants, the "Lightning F.1A" and "F.2", were steady but relatively minor refinements of the design; the next variant, the "Lightning F.3", was a major departure. The F.3 had higher thrust Rolls-Royce Avon 301R engines, a larger squared-off fin and strengthened inlet cone allowing a service clearance to (the F.1, F.1A and F.2 were limited to ). The A.I.23B radar and Red Top missile offered a forward hemisphere attack capability and deletion of the nose cannon. The new engines and fin made the F.3 the highest performance Lightning yet, but with an even higher fuel consumption and resulting shorter range. The next variant, the "Lightning F.6", was already in development, but there was a need for an interim solution to partially address the F.3's shortcomings, the "F.3A".