The F-15 first flew in 1972, and fifty years later, the US Air Force is still flying F-15 Eagles in Europe. An upgraded model – the F-15EX Eagle II – is due to begin deploying in the next few months, potentially extending the lifespan of the F-15 until the 2050s, 90 years after the first F-15 took to the skies. Despite operating in every major conflict of the last forty years and scoring more than 100 kills, an F-15 has never been downed by enemy action. So what makes the F-15 Eagle so formidable? And are we justified in suggesting that the F-15 is the greatest fighter jet of all time?