I do know that FedEx offer a "next available plane" service, at very considerable cost, which does essentially the same thing. A courier drives the package to LHR, where it's put on the next available flight (the time I was involved in using it, to Hong Kong). It's then met as the plane lands and driven straight to the recipient. It makes Hong Kong next day rather than two days, essentially, but the price is more than a round trip in economy. And that's the point - it's probably cheaper, and certainly more reliable, to send an office junior.