Mustangs never underpowered
In fact, the A and B models with the Allison engine could whip the pants off anything “under 12,000 feet.” But the military needed bomber escort planes that could fly effectively over twice as high. That's when the British started modifying their Mustangs with Rolls Royce Merlin engines that were equipped with superchargers that solved the problem — and the Americans followed in short order.
Otherwise, I really appreciated the D-Day coverage.
Major USAF (Retired)